Squashed 'third_party/GSL/' content from commit 0cebbd7

Change-Id: Iffb2e32f2f45297ac6d3e82168cd9df4ac5acc2f
git-subtree-dir: third_party/GSL
git-subtree-split: 0cebbd77bfc21acbf1cc05983ad626539eeeb8e0
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
new file mode 100644
index 0000000..b5e9bb2
--- /dev/null
+++ b/tests/CMakeLists.txt
@@ -0,0 +1,170 @@
+cmake_minimum_required(VERSION 2.8.7)
+
+project(GSLTests CXX)
+
+# will make visual studio generated project group files
+set_property(GLOBAL PROPERTY USE_FOLDERS ON)
+
+list(APPEND CATCH_CMAKE_ARGS
+    "-DCMAKE_INSTALL_PREFIX=${CMAKE_BINARY_DIR}/external"
+    "-DNO_SELFTEST=true"
+)
+
+if(GIT_FOUND)
+    # add catch
+    ExternalProject_Add(
+        catch
+        PREFIX ${CMAKE_BINARY_DIR}/catch
+        GIT_REPOSITORY https://github.com/catchorg/Catch2.git
+        GIT_TAG v2.0.1
+        CMAKE_ARGS ${CATCH_CMAKE_ARGS}
+        LOG_DOWNLOAD 1
+        UPDATE_DISCONNECTED 1
+    )
+else()
+    # assume catch is installed in a system directory
+    add_custom_target(catch)
+endif()
+
+if (MSVC AND (GSL_CXX_STANDARD EQUAL 17))
+    set(GSL_CPLUSPLUS_OPT -Zc:__cplusplus)
+endif()
+
+# this interface adds compile options to how the tests are run
+# please try to keep entries ordered =)
+add_library(gsl_tests_config INTERFACE)
+target_compile_options(gsl_tests_config INTERFACE
+    $<$<CXX_COMPILER_ID:MSVC>:
+        /EHsc
+        /W4
+        /WX
+    >
+    ${GSL_CPLUSPLUS_OPT}
+    $<$<NOT:$<CXX_COMPILER_ID:MSVC>>:
+        -fno-strict-aliasing
+        -Wall
+        -Wcast-align
+        -Wconversion
+        -Wctor-dtor-privacy
+        -Werror
+        -Wextra
+        -Wno-missing-braces
+        -Wnon-virtual-dtor
+        -Wold-style-cast
+        -Woverloaded-virtual
+        -Wpedantic
+        -Wshadow
+        -Wsign-conversion
+    >
+)
+
+# for tests to find the catch header
+target_include_directories(gsl_tests_config INTERFACE
+    ${CMAKE_BINARY_DIR}/external/include
+)
+
+# set definitions for tests
+target_compile_definitions(gsl_tests_config INTERFACE
+    GSL_THROW_ON_CONTRACT_VIOLATION
+)
+
+# create the main executable for each test. this reduces the compile time
+# of each test by pre-compiling catch.
+add_library(test_catch STATIC test.cpp)
+target_link_libraries(test_catch
+    GSL
+    gsl_tests_config
+)
+add_dependencies(test_catch catch)
+set_property(TARGET test_catch PROPERTY FOLDER "GSL_tests")
+
+function(add_gsl_test name)
+    add_executable(${name} ${name}.cpp)
+    target_link_libraries(${name}
+        GSL
+        test_catch
+        gsl_tests_config
+    )
+    add_dependencies(${name} catch)
+    add_test(
+      ${name}
+      ${name}
+    )
+    # group all tests under GSL_tests
+    set_property(TARGET ${name} PROPERTY FOLDER "GSL_tests")
+endfunction()
+
+add_gsl_test(span_tests)
+add_gsl_test(multi_span_tests)
+add_gsl_test(strided_span_tests)
+add_gsl_test(string_span_tests)
+add_gsl_test(at_tests)
+add_gsl_test(bounds_tests)
+add_gsl_test(notnull_tests)
+add_gsl_test(assertion_tests)
+add_gsl_test(utils_tests)
+add_gsl_test(owner_tests)
+add_gsl_test(byte_tests)
+add_gsl_test(algorithm_tests)
+
+
+# No exception tests
+
+foreach(flag_var
+        CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE
+        CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO)
+    STRING (REGEX REPLACE "/EHsc" "" ${flag_var} "${${flag_var}}")
+endforeach(flag_var)
+
+# this interface adds compile options to how the tests are run
+# please try to keep entries ordered =)
+add_library(gsl_tests_config_noexcept INTERFACE)
+target_compile_options(gsl_tests_config_noexcept INTERFACE
+    $<$<CXX_COMPILER_ID:MSVC>:
+        /D_HAS_EXCEPTIONS=0
+        /wd4702
+        /wd4577
+        /W4
+        /WX
+    >
+    ${GSL_CPLUSPLUS_OPT}
+    $<$<NOT:$<CXX_COMPILER_ID:MSVC>>:
+        -fno-strict-aliasing
+        -fno-exceptions
+        -Wall
+        -Wcast-align
+        -Wconversion
+        -Wctor-dtor-privacy
+        -Werror
+        -Wextra
+        -Wno-missing-braces
+        -Wnon-virtual-dtor
+        -Wold-style-cast
+        -Woverloaded-virtual
+        -Wpedantic
+        -Wshadow
+        -Wsign-conversion
+    >
+)
+
+# set definitions for tests
+target_compile_definitions(gsl_tests_config_noexcept INTERFACE
+    GSL_TERMINATE_ON_CONTRACT_VIOLATION
+)
+
+function(add_gsl_test_noexcept name)
+    add_executable(${name} ${name}.cpp)
+    target_link_libraries(${name}
+        GSL
+        gsl_tests_config_noexcept
+    )
+    add_test(
+      ${name}
+      ${name}
+    )
+    # group all tests under GSL_tests_noexcept
+    set_property(TARGET ${name} PROPERTY FOLDER "GSL_tests_noexcept")
+endfunction()
+
+add_gsl_test_noexcept(no_exception_throw_tests)
+add_gsl_test_noexcept(no_exception_ensure_tests)
diff --git a/tests/algorithm_tests.cpp b/tests/algorithm_tests.cpp
new file mode 100644
index 0000000..388d17d
--- /dev/null
+++ b/tests/algorithm_tests.cpp
@@ -0,0 +1,210 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <catch/catch.hpp> // for AssertionHandler, StringRef, CHECK, CHE...
+
+#include <gsl/gsl_algorithm> // for copy
+#include <gsl/span>          // for span
+
+#include <array>   // for array
+#include <cstddef> // for size_t
+
+namespace gsl {
+struct fail_fast;
+}  // namespace gsl
+
+using namespace std;
+using namespace gsl;
+
+TEST_CASE("same_type")
+{
+    // dynamic source and destination span
+    {
+        std::array<int, 5> src{1, 2, 3, 4, 5};
+        std::array<int, 10> dst{};
+
+        span<int> src_span(src);
+        span<int> dst_span(dst);
+
+        copy(src_span, dst_span);
+        copy(src_span, dst_span.subspan(src_span.size()));
+
+        for (std::size_t i = 0; i < src.size(); ++i) {
+            CHECK(dst[i] == src[i]);
+            CHECK(dst[i + src.size()] == src[i]);
+        }
+    }
+
+    // static source and dynamic destination span
+    {
+        std::array<int, 5> src{1, 2, 3, 4, 5};
+        std::array<int, 10> dst{};
+
+        span<int, 5> src_span(src);
+        span<int> dst_span(dst);
+
+        copy(src_span, dst_span);
+        copy(src_span, dst_span.subspan(src_span.size()));
+
+        for (std::size_t i = 0; i < src.size(); ++i) {
+            CHECK(dst[i] == src[i]);
+            CHECK(dst[i + src.size()] == src[i]);
+        }
+    }
+
+    // dynamic source and static destination span
+    {
+        std::array<int, 5> src{1, 2, 3, 4, 5};
+        std::array<int, 10> dst{};
+
+        span<int> src_span(src);
+        span<int, 10> dst_span(dst);
+
+        copy(src_span, dst_span);
+        copy(src_span, dst_span.subspan(src_span.size()));
+
+        for (std::size_t i = 0; i < src.size(); ++i) {
+            CHECK(dst[i] == src[i]);
+            CHECK(dst[i + src.size()] == src[i]);
+        }
+    }
+
+    // static source and destination span
+    {
+        std::array<int, 5> src{1, 2, 3, 4, 5};
+        std::array<int, 10> dst{};
+
+        span<int, 5> src_span(src);
+        span<int, 10> dst_span(dst);
+
+        copy(src_span, dst_span);
+        copy(src_span, dst_span.subspan(src_span.size()));
+
+        for (std::size_t i = 0; i < src.size(); ++i) {
+            CHECK(dst[i] == src[i]);
+            CHECK(dst[i + src.size()] == src[i]);
+        }
+    }
+}
+
+TEST_CASE("compatible_type")
+{
+    // dynamic source and destination span
+    {
+        std::array<short, 5> src{1, 2, 3, 4, 5};
+        std::array<int, 10> dst{};
+
+        span<short> src_span(src);
+        span<int> dst_span(dst);
+
+        copy(src_span, dst_span);
+        copy(src_span, dst_span.subspan(src_span.size()));
+
+        for (std::size_t i = 0; i < src.size(); ++i) {
+            CHECK(dst[i] == src[i]);
+            CHECK(dst[i + src.size()] == src[i]);
+        }
+    }
+
+    // static source and dynamic destination span
+    {
+        std::array<short, 5> src{1, 2, 3, 4, 5};
+        std::array<int, 10> dst{};
+
+        span<short, 5> src_span(src);
+        span<int> dst_span(dst);
+
+        copy(src_span, dst_span);
+        copy(src_span, dst_span.subspan(src_span.size()));
+
+        for (std::size_t i = 0; i < src.size(); ++i) {
+            CHECK(dst[i] == src[i]);
+            CHECK(dst[i + src.size()] == src[i]);
+        }
+    }
+
+    // dynamic source and static destination span
+    {
+        std::array<short, 5> src{1, 2, 3, 4, 5};
+        std::array<int, 10> dst{};
+
+        span<short> src_span(src);
+        span<int, 10> dst_span(dst);
+
+        copy(src_span, dst_span);
+        copy(src_span, dst_span.subspan(src_span.size()));
+
+        for (std::size_t i = 0; i < src.size(); ++i) {
+            CHECK(dst[i] == src[i]);
+            CHECK(dst[i + src.size()] == src[i]);
+        }
+    }
+
+    // static source and destination span
+    {
+        std::array<short, 5> src{1, 2, 3, 4, 5};
+        std::array<int, 10> dst{};
+
+        span<short, 5> src_span(src);
+        span<int, 10> dst_span(dst);
+
+        copy(src_span, dst_span);
+        copy(src_span, dst_span.subspan(src_span.size()));
+
+        for (std::size_t i = 0; i < src.size(); ++i) {
+            CHECK(dst[i] == src[i]);
+            CHECK(dst[i + src.size()] == src[i]);
+        }
+    }
+}
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+TEST_CASE("incompatible_type")
+{
+    std::array<int, 4> src{1, 2, 3, 4};
+    std::array<int*, 12> dst{};
+
+    span<int> src_span_dyn(src);
+    span<int, 4> src_span_static(src);
+    span<int*> dst_span_dyn(dst);
+    span<int*, 4> dst_span_static(dst);
+
+    // every line should produce a compilation error
+    copy(src_span_dyn, dst_span_dyn);
+    copy(src_span_dyn, dst_span_static);
+    copy(src_span_static, dst_span_dyn);
+    copy(src_span_static, dst_span_static);
+}
+#endif
+
+TEST_CASE("small_destination_span")
+{
+    std::array<int, 12> src{1, 2, 3, 4};
+    std::array<int, 4> dst{};
+
+    span<int> src_span_dyn(src);
+    span<int, 12> src_span_static(src);
+    span<int> dst_span_dyn(dst);
+    span<int, 4> dst_span_static(dst);
+
+    CHECK_THROWS_AS(copy(src_span_dyn, dst_span_dyn), fail_fast);
+    CHECK_THROWS_AS(copy(src_span_dyn, dst_span_static), fail_fast);
+    CHECK_THROWS_AS(copy(src_span_static, dst_span_dyn), fail_fast);
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+    copy(src_span_static, dst_span_static);
+#endif
+}
diff --git a/tests/assertion_tests.cpp b/tests/assertion_tests.cpp
new file mode 100644
index 0000000..25c0089
--- /dev/null
+++ b/tests/assertion_tests.cpp
@@ -0,0 +1,46 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <catch/catch.hpp> // for AssertionHandler, StringRef, CHECK, CHECK...
+
+#include <gsl/gsl_assert> // for fail_fast (ptr only), Ensures, Expects
+
+using namespace gsl;
+
+int f(int i)
+{
+    Expects(i > 0 && i < 10);
+    return i;
+}
+
+TEST_CASE("expects")
+{
+    CHECK(f(2) == 2);
+    CHECK_THROWS_AS(f(10), fail_fast);
+}
+
+int g(int i)
+{
+    i++;
+    Ensures(i > 0 && i < 10);
+    return i;
+}
+
+TEST_CASE("ensures")
+{
+    CHECK(g(2) == 3);
+    CHECK_THROWS_AS(g(9), fail_fast);
+}
diff --git a/tests/at_tests.cpp b/tests/at_tests.cpp
new file mode 100644
index 0000000..2f9e999
--- /dev/null
+++ b/tests/at_tests.cpp
@@ -0,0 +1,116 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <catch/catch.hpp> // for AssertionHandler, StringRef, CHECK_THROW...
+
+#include <gsl/gsl_util> // for at
+
+#include <array>            // for array
+#include <cstddef>          // for size_t
+#include <initializer_list> // for initializer_list
+#include <vector>           // for vector
+
+namespace gsl {
+struct fail_fast;
+}  // namespace gsl
+
+using gsl::fail_fast;
+
+TEST_CASE("static_array")
+{
+    int a[4] = {1, 2, 3, 4};
+    const int(&c_a)[4] = a;
+
+    for (int i = 0; i < 4; ++i) {
+        CHECK(&gsl::at(a, i) == &a[i]);
+        CHECK(&gsl::at(c_a, i) == &a[i]);
+    }
+
+    CHECK_THROWS_AS(gsl::at(a, -1), fail_fast);
+    CHECK_THROWS_AS(gsl::at(a, 4), fail_fast);
+    CHECK_THROWS_AS(gsl::at(c_a, -1), fail_fast);
+    CHECK_THROWS_AS(gsl::at(c_a, 4), fail_fast);
+}
+
+TEST_CASE("std_array")
+{
+    std::array<int, 4> a = {1, 2, 3, 4};
+    const std::array<int, 4>& c_a = a;
+
+    for (int i = 0; i < 4; ++i) {
+        CHECK(&gsl::at(a, i) == &a[static_cast<std::size_t>(i)]);
+        CHECK(&gsl::at(c_a, i) == &a[static_cast<std::size_t>(i)]);
+    }
+
+    CHECK_THROWS_AS(gsl::at(a, -1), fail_fast);
+    CHECK_THROWS_AS(gsl::at(a, 4), fail_fast);
+    CHECK_THROWS_AS(gsl::at(c_a, -1), fail_fast);
+    CHECK_THROWS_AS(gsl::at(c_a, 4), fail_fast);
+}
+
+TEST_CASE("StdVector")
+{
+    std::vector<int> a = {1, 2, 3, 4};
+    const std::vector<int>& c_a = a;
+
+    for (int i = 0; i < 4; ++i) {
+        CHECK(&gsl::at(a, i) == &a[static_cast<std::size_t>(i)]);
+        CHECK(&gsl::at(c_a, i) == &a[static_cast<std::size_t>(i)]);
+    }
+
+    CHECK_THROWS_AS(gsl::at(a, -1), fail_fast);
+    CHECK_THROWS_AS(gsl::at(a, 4), fail_fast);
+    CHECK_THROWS_AS(gsl::at(c_a, -1), fail_fast);
+    CHECK_THROWS_AS(gsl::at(c_a, 4), fail_fast);
+}
+
+TEST_CASE("InitializerList")
+{
+    std::initializer_list<int> a = {1, 2, 3, 4};
+
+    for (int i = 0; i < 4; ++i) {
+        CHECK(gsl::at(a, i) == i + 1);
+        CHECK(gsl::at({1, 2, 3, 4}, i) == i + 1);
+    }
+
+    CHECK_THROWS_AS(gsl::at(a, -1), fail_fast);
+    CHECK_THROWS_AS(gsl::at(a, 4), fail_fast);
+    CHECK_THROWS_AS(gsl::at({1, 2, 3, 4}, -1), fail_fast);
+    CHECK_THROWS_AS(gsl::at({1, 2, 3, 4}, 4), fail_fast);
+}
+
+#if !defined(_MSC_VER) || defined(__clang__) || _MSC_VER >= 1910
+static constexpr bool test_constexpr()
+{
+    int a1[4] = {1, 2, 3, 4};
+    const int(&c_a1)[4] = a1;
+    std::array<int, 4> a2 = {1, 2, 3, 4};
+    const std::array<int, 4>& c_a2 = a2;
+
+    for (int i = 0; i < 4; ++i) {
+        if (&gsl::at(a1, i) != &a1[i]) return false;
+        if (&gsl::at(c_a1, i) != &a1[i]) return false;
+        // requires C++17:
+        // if (&gsl::at(a2, i) != &a2[static_cast<std::size_t>(i)]) return false;
+        if (&gsl::at(c_a2, i) != &c_a2[static_cast<std::size_t>(i)]) return false;
+        if (gsl::at({1, 2, 3, 4}, i) != i + 1) return false;
+    }
+
+    return true;
+}
+
+static_assert(test_constexpr(), "FAIL");
+#endif
diff --git a/tests/bounds_tests.cpp b/tests/bounds_tests.cpp
new file mode 100644
index 0000000..1f4b1e2
--- /dev/null
+++ b/tests/bounds_tests.cpp
@@ -0,0 +1,99 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <catch/catch.hpp> // for AssertionHandler, StringRef, TEST_CASE
+
+#include <gsl/multi_span> // for static_bounds, static_bounds_dynamic_range_t
+
+#include <cstddef> // for ptrdiff_t, size_t
+
+namespace gsl {
+struct fail_fast;
+}  // namespace gsl
+
+using namespace std;
+using namespace gsl;
+
+namespace
+{
+void use(std::ptrdiff_t&) {}
+}
+
+TEST_CASE("basic_bounds")
+{
+    for (auto point : static_bounds<dynamic_range, 3, 4>{2}) {
+        for (decltype(point)::size_type j = 0;
+             j < static_cast<decltype(point)::size_type>(decltype(point)::rank); j++)
+        {
+            use(j);
+            use(point[static_cast<std::size_t>(j)]);
+        }
+    }
+}
+
+TEST_CASE("bounds_basic")
+{
+    static_bounds<3, 4, 5> b;
+    const auto a = b.slice();
+    (void) a;
+    static_bounds<4, dynamic_range, 2> x{4};
+    x.slice().slice();
+}
+
+TEST_CASE("arrayview_iterator")
+{
+    static_bounds<4, dynamic_range, 2> bounds{3};
+
+    const auto itr = bounds.begin();
+    (void) itr;
+#ifdef CONFIRM_COMPILATION_ERRORS
+    multi_span<int, 4, dynamic_range, 2> av(nullptr, bounds);
+
+    auto itr2 = av.cbegin();
+
+    for (auto& v : av) {
+        v = 4;
+    }
+    fill(av.begin(), av.end(), 0);
+#endif
+}
+
+TEST_CASE("bounds_convertible")
+{
+    static_bounds<7, 4, 2> b1;
+    static_bounds<7, dynamic_range, 2> b2 = b1;
+    (void) b2;
+#ifdef CONFIRM_COMPILATION_ERRORS
+    static_bounds<7, dynamic_range, 1> b4 = b2;
+#endif
+
+    static_bounds<dynamic_range, dynamic_range, dynamic_range> b3 = b1;
+    static_bounds<7, 4, 2> b4 = b3;
+    (void) b4;
+
+    static_bounds<dynamic_range> b11;
+
+    static_bounds<dynamic_range> b5;
+    static_bounds<34> b6;
+
+    b5 = static_bounds<20>();
+    CHECK_THROWS_AS(b6 = b5, fail_fast);
+    b5 = static_bounds<34>();
+    b6 = b5;
+
+    CHECK(b5 == b6);
+    CHECK(b5.size() == b6.size());
+}
diff --git a/tests/byte_tests.cpp b/tests/byte_tests.cpp
new file mode 100644
index 0000000..41501ce
--- /dev/null
+++ b/tests/byte_tests.cpp
@@ -0,0 +1,124 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <catch/catch.hpp> // for AssertionHandler, StringRef, CHECK, TEST_...
+
+#include <gsl/gsl_byte> // for to_byte, to_integer, byte, operator&, ope...
+
+using namespace std;
+using namespace gsl;
+
+namespace
+{
+
+TEST_CASE("construction")
+{
+    {
+        const byte b = static_cast<byte>(4);
+        CHECK(static_cast<unsigned char>(b) == 4);
+    }
+
+    {
+        const byte b = byte(12);
+        CHECK(static_cast<unsigned char>(b) == 12);
+    }
+
+    {
+        const byte b = to_byte<12>();
+        CHECK(static_cast<unsigned char>(b) == 12);
+    }
+    {
+        const unsigned char uc = 12;
+        const byte b = to_byte(uc);
+        CHECK(static_cast<unsigned char>(b) == 12);
+    }
+
+    // waiting for C++17 enum class direct initializer support
+    //{
+    //    byte b { 14 };
+    //    CHECK(static_cast<unsigned char>(b) == 14);
+    //}
+}
+
+TEST_CASE("bitwise_operations")
+{
+    const byte b = to_byte<0xFF>();
+
+    byte a = to_byte<0x00>();
+    CHECK((b | a) == to_byte<0xFF>());
+    CHECK(a == to_byte<0x00>());
+
+    a |= b;
+    CHECK(a == to_byte<0xFF>());
+
+    a = to_byte<0x01>();
+    CHECK((b & a) == to_byte<0x01>());
+
+    a &= b;
+    CHECK(a == to_byte<0x01>());
+
+    CHECK((b ^ a) == to_byte<0xFE>());
+
+    CHECK(a == to_byte<0x01>());
+    a ^= b;
+    CHECK(a == to_byte<0xFE>());
+
+    a = to_byte<0x01>();
+    CHECK(~a == to_byte<0xFE>());
+
+    a = to_byte<0xFF>();
+    CHECK((a << 4) == to_byte<0xF0>());
+    CHECK((a >> 4) == to_byte<0x0F>());
+
+    a <<= 4;
+    CHECK(a == to_byte<0xF0>());
+    a >>= 4;
+    CHECK(a == to_byte<0x0F>());
+}
+
+TEST_CASE("to_integer")
+{
+    const byte b = to_byte<0x12>();
+
+    CHECK(0x12 == gsl::to_integer<char>(b));
+    CHECK(0x12 == gsl::to_integer<short>(b));
+    CHECK(0x12 == gsl::to_integer<long>(b));
+    CHECK(0x12 == gsl::to_integer<long long>(b));
+
+    CHECK(0x12 == gsl::to_integer<unsigned char>(b));
+    CHECK(0x12 == gsl::to_integer<unsigned short>(b));
+    CHECK(0x12 == gsl::to_integer<unsigned long>(b));
+    CHECK(0x12 == gsl::to_integer<unsigned long long>(b));
+
+    //      CHECK(0x12 == gsl::to_integer<float>(b));   // expect compile-time error
+    //      CHECK(0x12 == gsl::to_integer<double>(b));  // expect compile-time error
+}
+
+int modify_both(gsl::byte & b, int& i)
+{
+    i = 10;
+    b = to_byte<5>();
+    return i;
+}
+
+TEST_CASE("aliasing")
+{
+    int i{0};
+    const int res = modify_both(reinterpret_cast<byte&>(i), i);
+    CHECK(res == i);
+}
+
+}
diff --git a/tests/multi_span_tests.cpp b/tests/multi_span_tests.cpp
new file mode 100644
index 0000000..549dcbe
--- /dev/null
+++ b/tests/multi_span_tests.cpp
@@ -0,0 +1,1701 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <catch/catch.hpp> // for AssertionHandler, StringRef, CHECK, CHECK...
+
+#include <gsl/gsl_byte>   // for byte
+#include <gsl/gsl_util>   // for narrow_cast
+#include <gsl/multi_span> // for multi_span, contiguous_span_iterator, dim
+
+#include <algorithm> // for fill, for_each
+#include <array>     // for array
+#include <iostream>  // for ptrdiff_t, size_t
+#include <iterator>  // for reverse_iterator, begin, end, operator!=
+#include <numeric>   // for iota
+#include <stddef.h>  // for ptrdiff_t
+#include <string>    // for string
+#include <vector>    // for vector
+
+namespace gsl {
+struct fail_fast;
+}  // namespace gsl
+
+using namespace std;
+using namespace gsl;
+
+namespace
+{
+struct BaseClass
+{
+};
+struct DerivedClass : BaseClass
+{
+};
+}
+
+TEST_CASE("default_constructor")
+{
+    {
+        multi_span<int> s;
+        CHECK((s.length() == 0 && s.data() == nullptr));
+
+        multi_span<const int> cs;
+        CHECK((cs.length() == 0 && cs.data() == nullptr));
+    }
+
+    {
+        multi_span<int, 0> s;
+        CHECK((s.length() == 0 && s.data() == nullptr));
+
+        multi_span<const int, 0> cs;
+        CHECK((cs.length() == 0 && cs.data() == nullptr));
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<int, 1> s;
+        CHECK((s.length() == 1 && s.data() == nullptr)); // explains why it can't compile
+#endif
+    }
+
+    {
+        multi_span<int> s{};
+        CHECK((s.length() == 0 && s.data() == nullptr));
+
+        multi_span<const int> cs{};
+        CHECK((cs.length() == 0 && cs.data() == nullptr));
+    }
+}
+
+TEST_CASE("from_nullptr_constructor")
+{
+    {
+        multi_span<int> s = nullptr;
+        CHECK((s.length() == 0 && s.data() == nullptr));
+
+        multi_span<const int> cs = nullptr;
+        CHECK((cs.length() == 0 && cs.data() == nullptr));
+    }
+
+    {
+        multi_span<int, 0> s = nullptr;
+        CHECK((s.length() == 0 && s.data() == nullptr));
+
+        multi_span<const int, 0> cs = nullptr;
+        CHECK((cs.length() == 0 && cs.data() == nullptr));
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<int, 1> s = nullptr;
+        CHECK((s.length() == 1 && s.data() == nullptr)); // explains why it can't compile
+#endif
+    }
+
+    {
+        multi_span<int> s{nullptr};
+        CHECK((s.length() == 0 && s.data() == nullptr));
+
+        multi_span<const int> cs{nullptr};
+        CHECK((cs.length() == 0 && cs.data() == nullptr));
+    }
+
+    {
+        multi_span<int*> s{nullptr};
+        CHECK((s.length() == 0 && s.data() == nullptr));
+
+        multi_span<const int*> cs{nullptr};
+        CHECK((cs.length() == 0 && cs.data() == nullptr));
+    }
+}
+
+TEST_CASE("from_nullptr_length_constructor")
+{
+    {
+        multi_span<int> s{nullptr, 0};
+        CHECK((s.length() == 0 && s.data() == nullptr));
+
+        multi_span<const int> cs{nullptr, 0};
+        CHECK((cs.length() == 0 && cs.data() == nullptr));
+    }
+
+    {
+        multi_span<int, 0> s{nullptr, 0};
+        CHECK((s.length() == 0 && s.data() == nullptr));
+
+        multi_span<const int, 0> cs{nullptr, 0};
+        CHECK((cs.length() == 0 && cs.data() == nullptr));
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<int, 1> s{nullptr, 0};
+        CHECK((s.length() == 1 && s.data() == nullptr)); // explains why it can't compile
+#endif
+    }
+
+    {
+        auto workaround_macro = []() { multi_span<int> s{nullptr, 1}; };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+
+        auto const_workaround_macro = []() { multi_span<const int> cs{nullptr, 1}; };
+        CHECK_THROWS_AS(const_workaround_macro(), fail_fast);
+    }
+
+    {
+        auto workaround_macro = []() { multi_span<int, 0> s{nullptr, 1}; };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+
+        auto const_workaround_macro = []() { multi_span<const int, 0> s{nullptr, 1}; };
+        CHECK_THROWS_AS(const_workaround_macro(), fail_fast);
+    }
+
+    {
+        multi_span<int*> s{nullptr, 0};
+        CHECK((s.length() == 0 && s.data() == nullptr));
+
+        multi_span<const int*> cs{nullptr, 0};
+        CHECK((cs.length() == 0 && cs.data() == nullptr));
+    }
+}
+
+TEST_CASE("from_element_constructor")
+{
+    int i = 5;
+
+    {
+        multi_span<int> s = i;
+        CHECK((s.length() == 1 && s.data() == &i));
+        CHECK(s[0] == 5);
+
+        multi_span<const int> cs = i;
+        CHECK((cs.length() == 1 && cs.data() == &i));
+        CHECK(cs[0] == 5);
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        const j = 1;
+        multi_span<int, 0> s = j;
+#endif
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<int, 0> s = i;
+        CHECK((s.length() == 0 && s.data() == &i));
+#endif
+    }
+
+    {
+        multi_span<int, 1> s = i;
+        CHECK((s.length() == 1 && s.data() == &i));
+        CHECK(s[0] == 5);
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<int, 2> s = i;
+        CHECK((s.length() == 2 && s.data() == &i));
+#endif
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        auto get_a_temp = []() -> int { return 4; };
+        auto use_a_span = [](multi_span<int> s) { (void) s; };
+        use_a_span(get_a_temp());
+#endif
+    }
+}
+
+TEST_CASE("from_pointer_length_constructor")
+{
+    int arr[4] = {1, 2, 3, 4};
+
+    {
+        multi_span<int> s{&arr[0], 2};
+        CHECK((s.length() == 2 && s.data() == &arr[0]));
+        CHECK((s[0] == 1 && s[1] == 2));
+    }
+
+    {
+        multi_span<int, 2> s{&arr[0], 2};
+        CHECK((s.length() == 2 && s.data() == &arr[0]));
+        CHECK((s[0] == 1 && s[1] == 2));
+    }
+
+    {
+        int* p = nullptr;
+        multi_span<int> s{p, 0};
+        CHECK((s.length() == 0 && s.data() == nullptr));
+    }
+
+    {
+        int* p = nullptr;
+        auto workaround_macro = [=]() { multi_span<int> s{p, 2}; };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    }
+}
+
+TEST_CASE("from_pointer_pointer_constructor")
+{
+    int arr[4] = {1, 2, 3, 4};
+
+    {
+        multi_span<int> s{&arr[0], &arr[2]};
+        CHECK((s.length() == 2 && s.data() == &arr[0]));
+        CHECK((s[0] == 1 && s[1] == 2));
+    }
+
+    {
+        multi_span<int, 2> s{&arr[0], &arr[2]};
+        CHECK((s.length() == 2 && s.data() == &arr[0]));
+        CHECK((s[0] == 1 && s[1] == 2));
+    }
+
+    {
+        multi_span<int> s{&arr[0], &arr[0]};
+        CHECK((s.length() == 0 && s.data() == &arr[0]));
+    }
+
+    {
+        multi_span<int, 0> s{&arr[0], &arr[0]};
+        CHECK((s.length() == 0 && s.data() == &arr[0]));
+    }
+
+    {
+        auto workaround_macro = [&]() { multi_span<int> s{&arr[1], &arr[0]}; };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    }
+
+    {
+        int* p = nullptr;
+        auto workaround_macro = [&]() { multi_span<int> s{&arr[0], p}; };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    }
+
+    {
+        int* p = nullptr;
+        auto workaround_macro = [&]() { multi_span<int> s{p, p}; };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    }
+
+    {
+        int* p = nullptr;
+        auto workaround_macro = [&]() { multi_span<int> s{&arr[0], p}; };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    }
+}
+
+TEST_CASE("from_array_constructor")
+{
+    int arr[5] = {1, 2, 3, 4, 5};
+
+    {
+        multi_span<int> s{arr};
+        CHECK((s.length() == 5 && s.data() == &arr[0]));
+    }
+
+    {
+        multi_span<int, 5> s{arr};
+        CHECK((s.length() == 5 && s.data() == &arr[0]));
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<int, 6> s{arr};
+#endif
+    }
+
+    {
+        multi_span<int, 0> s{arr};
+        CHECK((s.length() == 0 && s.data() == &arr[0]));
+    }
+
+    int arr2d[2][3] = {1, 2, 3, 4, 5, 6};
+
+    {
+        multi_span<int> s{arr2d};
+        CHECK((s.length() == 6 && s.data() == &arr2d[0][0]));
+        CHECK((s[0] == 1 && s[5] == 6));
+    }
+
+    {
+        multi_span<int, 0> s{arr2d};
+        CHECK((s.length() == 0 && s.data() == &arr2d[0][0]));
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<int, 5> s{arr2d};
+#endif
+    }
+
+    {
+        multi_span<int, 6> s{arr2d};
+        CHECK((s.length() == 6 && s.data() == &arr2d[0][0]));
+        CHECK((s[0] == 1 && s[5] == 6));
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<int, 7> s{arr2d};
+#endif
+    }
+
+    {
+        multi_span<int[3]> s{arr2d[0]};
+        CHECK((s.length() == 1 && s.data() == &arr2d[0]));
+    }
+
+    {
+        multi_span<int, 2, 3> s{arr2d};
+        CHECK((s.length() == 6 && s.data() == &arr2d[0][0]));
+        auto workaround_macro = [&]() { return s[{1, 2}] == 6; };
+        CHECK(workaround_macro());
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<int, 3, 3> s{arr2d};
+#endif
+    }
+
+    int arr3d[2][3][2] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
+
+    {
+        multi_span<int> s{arr3d};
+        CHECK((s.length() == 12 && s.data() == &arr3d[0][0][0]));
+        CHECK((s[0] == 1 && s[11] == 12));
+    }
+
+    {
+        multi_span<int, 0> s{arr3d};
+        CHECK((s.length() == 0 && s.data() == &arr3d[0][0][0]));
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<int, 11> s{arr3d};
+#endif
+    }
+
+    {
+        multi_span<int, 12> s{arr3d};
+        CHECK((s.length() == 12 && s.data() == &arr3d[0][0][0]));
+        CHECK((s[0] == 1 && s[5] == 6));
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<int, 13> s{arr3d};
+#endif
+    }
+
+    {
+        multi_span<int[3][2]> s{arr3d[0]};
+        CHECK((s.length() == 1 && s.data() == &arr3d[0]));
+    }
+
+    {
+        multi_span<int, 3, 2, 2> s{arr3d};
+        CHECK((s.length() == 12 && s.data() == &arr3d[0][0][0]));
+        auto workaround_macro = [&]() { return s[{2, 1, 0}] == 11; };
+        CHECK(workaround_macro());
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<int, 3, 3, 3> s{arr3d};
+#endif
+    }
+}
+
+TEST_CASE("from_dynamic_array_constructor")
+{
+    double(*arr)[3][4] = new double[100][3][4];
+
+    {
+        multi_span<double, dynamic_range, 3, 4> s(arr, 10);
+        CHECK((s.length() == 120 && s.data() == &arr[0][0][0]));
+        CHECK_THROWS_AS(s[10][3][4], fail_fast);
+    }
+
+    {
+        multi_span<double, dynamic_range, 4, 3> s(arr, 10);
+        CHECK((s.length() == 120 && s.data() == &arr[0][0][0]));
+    }
+
+    {
+        multi_span<double> s(arr, 10);
+        CHECK((s.length() == 120 && s.data() == &arr[0][0][0]));
+    }
+
+    {
+        multi_span<double, dynamic_range, 3, 4> s(arr, 0);
+        CHECK((s.length() == 0 && s.data() == &arr[0][0][0]));
+    }
+
+    delete[] arr;
+}
+
+TEST_CASE("from_std_array_constructor")
+{
+    std::array<int, 4> arr = {1, 2, 3, 4};
+
+    {
+        multi_span<int> s{arr};
+        CHECK((s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data()));
+
+        multi_span<const int> cs{arr};
+        CHECK((cs.size() == narrow_cast<ptrdiff_t>(arr.size()) && cs.data() == arr.data()));
+    }
+
+    {
+        multi_span<int, 4> s{arr};
+        CHECK((s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data()));
+
+        multi_span<const int, 4> cs{arr};
+        CHECK((cs.size() == narrow_cast<ptrdiff_t>(arr.size()) && cs.data() == arr.data()));
+    }
+
+    {
+        multi_span<int, 2> s{arr};
+        CHECK((s.size() == 2 && s.data() == arr.data()));
+
+        multi_span<const int, 2> cs{arr};
+        CHECK((cs.size() == 2 && cs.data() == arr.data()));
+    }
+
+    {
+        multi_span<int, 0> s{arr};
+        CHECK((s.size() == 0 && s.data() == arr.data()));
+
+        multi_span<const int, 0> cs{arr};
+        CHECK((cs.size() == 0 && cs.data() == arr.data()));
+    }
+
+    // TODO This is currently an unsupported scenario. We will come back to it as we revise
+    // the multidimensional interface and what transformations between dimensionality look like
+    //{
+    //    multi_span<int, 2, 2> s{arr};
+    //    CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
+    //}
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<int, 5> s{arr};
+#endif
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        auto get_an_array = []() { return std::array<int, 4>{1, 2, 3, 4}; };
+        auto take_a_span = [](multi_span<int> s) { (void) s; };
+        // try to take a temporary std::array
+        take_a_span(get_an_array());
+#endif
+    }
+}
+
+TEST_CASE("from_const_std_array_constructor")
+{
+    const std::array<int, 4> arr = {1, 2, 3, 4};
+
+    {
+        multi_span<const int> s{arr};
+        CHECK((s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data()));
+    }
+
+    {
+        multi_span<const int, 4> s{arr};
+        CHECK((s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data()));
+    }
+
+    {
+        multi_span<const int, 2> s{arr};
+        CHECK((s.size() == 2 && s.data() == arr.data()));
+    }
+
+    {
+        multi_span<const int, 0> s{arr};
+        CHECK((s.size() == 0 && s.data() == arr.data()));
+    }
+
+    // TODO This is currently an unsupported scenario. We will come back to it as we revise
+    // the multidimensional interface and what transformations between dimensionality look like
+    //{
+    //    multi_span<int, 2, 2> s{arr};
+    //    CHECK(s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data());
+    //}
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<const int, 5> s{arr};
+#endif
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        auto get_an_array = []() -> const std::array<int, 4> { return {1, 2, 3, 4}; };
+        auto take_a_span = [](multi_span<const int> s) { (void) s; };
+        // try to take a temporary std::array
+        take_a_span(get_an_array());
+#endif
+    }
+}
+
+TEST_CASE("from_container_constructor")
+{
+    std::vector<int> v = {1, 2, 3};
+    const std::vector<int> cv = v;
+
+    {
+        multi_span<int> s{v};
+        CHECK((s.size() == narrow_cast<std::ptrdiff_t>(v.size()) && s.data() == v.data()));
+
+        multi_span<const int> cs{v};
+        CHECK((cs.size() == narrow_cast<std::ptrdiff_t>(v.size()) && cs.data() == v.data()));
+    }
+
+    std::string str = "hello";
+    const std::string cstr = "hello";
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<char> s{str};
+        CHECK((s.size() == narrow_cast<std::ptrdiff_t>(str.size()) && s.data() == str.data()));
+#endif
+        multi_span<const char> cs{str};
+        CHECK((cs.size() == narrow_cast<std::ptrdiff_t>(str.size()) && cs.data() == str.data()));
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        multi_span<char> s{cstr};
+#endif
+        multi_span<const char> cs{cstr};
+        CHECK((cs.size() == narrow_cast<std::ptrdiff_t>(cstr.size()) &&
+               cs.data() == cstr.data()));
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        auto get_temp_vector = []() -> std::vector<int> { return {}; };
+        auto use_span = [](multi_span<int> s) { (void) s; };
+        use_span(get_temp_vector());
+#endif
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        auto get_temp_string = []() -> std::string { return {}; };
+        auto use_span = [](multi_span<char> s) { (void) s; };
+        use_span(get_temp_string());
+#endif
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        auto get_temp_vector = []() -> const std::vector<int> { return {}; };
+        auto use_span = [](multi_span<const char> s) { (void) s; };
+        use_span(get_temp_vector());
+#endif
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        auto get_temp_string = []() -> const std::string { return {}; };
+        auto use_span = [](multi_span<const char> s) { (void) s; };
+        use_span(get_temp_string());
+#endif
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        std::map<int, int> m;
+        multi_span<int> s{m};
+#endif
+    }
+}
+
+TEST_CASE("from_convertible_span_constructor")
+{
+#ifdef CONFIRM_COMPILATION_ERRORS
+    multi_span<int, 7, 4, 2> av1(nullptr, b1);
+
+    auto f = [&]() { multi_span<int, 7, 4, 2> av1(nullptr); };
+    CHECK_THROWS_AS(f(), fail_fast);
+#endif
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+    static_bounds<std::size_t, 7, dynamic_range, 2> b12(b11);
+    b12 = b11;
+    b11 = b12;
+
+    multi_span<int, dynamic_range> av1 = nullptr;
+    multi_span<int, 7, dynamic_range, 2> av2(av1);
+    multi_span<int, 7, 4, 2> av2(av1);
+#endif
+
+    multi_span<DerivedClass> avd;
+#ifdef CONFIRM_COMPILATION_ERRORS
+    multi_span<BaseClass> avb = avd;
+#endif
+    multi_span<const DerivedClass> avcd = avd;
+    (void) avcd;
+}
+
+TEST_CASE("copy_move_and_assignment")
+{
+    multi_span<int> s1;
+    CHECK(s1.empty());
+
+    int arr[] = {3, 4, 5};
+
+    multi_span<const int> s2 = arr;
+    CHECK((s2.length() == 3 && s2.data() == &arr[0]));
+
+    s2 = s1;
+    CHECK(s2.empty());
+
+    auto get_temp_span = [&]() -> multi_span<int> { return {&arr[1], 2}; };
+    auto use_span = [&](multi_span<const int> s) {
+        CHECK((s.length() == 2 && s.data() == &arr[1]));
+    };
+    use_span(get_temp_span());
+
+    s1 = get_temp_span();
+    CHECK((s1.length() == 2 && s1.data() == &arr[1]));
+}
+
+template <class Bounds>
+void fn(const Bounds&)
+{
+    static_assert(Bounds::static_size == 60, "static bounds is wrong size");
+}
+TEST_CASE("as_multi_span_reshape")
+{
+    int a[3][4][5];
+    auto av = as_multi_span(a);
+    fn(av.bounds());
+    auto av2 = as_multi_span(av, dim<60>());
+    auto av3 = as_multi_span(av2, dim<3>(), dim<4>(), dim<5>());
+    auto av4 = as_multi_span(av3, dim<4>(), dim(3), dim<5>());
+    auto av5 = as_multi_span(av4, dim<3>(), dim<4>(), dim<5>());
+    auto av6 = as_multi_span(av5, dim<12>(), dim(5));
+
+    fill(av6.begin(), av6.end(), 1);
+
+    auto av7 = as_bytes(av6);
+
+    auto av8 = as_multi_span<int>(av7);
+
+    CHECK(av8.size() == av6.size());
+    for (auto i = 0; i < av8.size(); i++) {
+        CHECK(av8[i] == 1);
+    }
+}
+
+TEST_CASE("first")
+{
+    int arr[5] = {1, 2, 3, 4, 5};
+
+    {
+        multi_span<int, 5> av = arr;
+        CHECK((av.first<2>().bounds() == static_bounds<2>()));
+        CHECK(av.first<2>().length() == 2);
+        CHECK(av.first(2).length() == 2);
+    }
+
+    {
+        multi_span<int, 5> av = arr;
+        CHECK((av.first<0>().bounds() == static_bounds<0>()));
+        CHECK(av.first<0>().length() == 0);
+        CHECK(av.first(0).length() == 0);
+    }
+
+    {
+        multi_span<int, 5> av = arr;
+        CHECK((av.first<5>().bounds() == static_bounds<5>()));
+        CHECK(av.first<5>().length() == 5);
+        CHECK(av.first(5).length() == 5);
+    }
+
+    {
+        multi_span<int, 5> av = arr;
+#ifdef CONFIRM_COMPILATION_ERRORS
+        CHECK(av.first<6>().bounds() == static_bounds<6>());
+        CHECK(av.first<6>().length() == 6);
+        CHECK(av.first<-1>().length() == -1);
+#endif
+        CHECK_THROWS_AS(av.first(6).length(), fail_fast);
+    }
+
+    {
+        multi_span<int, dynamic_range> av;
+        CHECK((av.first<0>().bounds() == static_bounds<0>()));
+        CHECK(av.first<0>().length() == 0);
+        CHECK(av.first(0).length() == 0);
+    }
+}
+
+TEST_CASE("last")
+{
+    int arr[5] = {1, 2, 3, 4, 5};
+
+    {
+        multi_span<int, 5> av = arr;
+        CHECK((av.last<2>().bounds() == static_bounds<2>()));
+        CHECK(av.last<2>().length() == 2);
+        CHECK(av.last(2).length() == 2);
+    }
+
+    {
+        multi_span<int, 5> av = arr;
+        CHECK((av.last<0>().bounds() == static_bounds<0>()));
+        CHECK(av.last<0>().length() == 0);
+        CHECK(av.last(0).length() == 0);
+    }
+
+    {
+        multi_span<int, 5> av = arr;
+        CHECK((av.last<5>().bounds() == static_bounds<5>()));
+        CHECK(av.last<5>().length() == 5);
+        CHECK(av.last(5).length() == 5);
+    }
+
+    {
+        multi_span<int, 5> av = arr;
+#ifdef CONFIRM_COMPILATION_ERRORS
+        CHECK((av.last<6>().bounds() == static_bounds<6>()));
+        CHECK(av.last<6>().length() == 6);
+#endif
+        CHECK_THROWS_AS(av.last(6).length(), fail_fast);
+    }
+
+    {
+        multi_span<int, dynamic_range> av;
+        CHECK((av.last<0>().bounds() == static_bounds<0>()));
+        CHECK(av.last<0>().length() == 0);
+        CHECK(av.last(0).length() == 0);
+    }
+}
+
+TEST_CASE("subspan")
+{
+    int arr[5] = {1, 2, 3, 4, 5};
+
+    {
+        multi_span<int, 5> av = arr;
+        CHECK((av.subspan<2, 2>().bounds() == static_bounds<2>()));
+        CHECK((av.subspan<2, 2>().length() == 2));
+        CHECK(av.subspan(2, 2).length() == 2);
+        CHECK(av.subspan(2, 3).length() == 3);
+    }
+
+    {
+        multi_span<int, 5> av = arr;
+        CHECK((av.subspan<0, 0>().bounds() == static_bounds<0>()));
+        CHECK((av.subspan<0, 0>().length() == 0));
+        CHECK(av.subspan(0, 0).length() == 0);
+    }
+
+    {
+        multi_span<int, 5> av = arr;
+        CHECK((av.subspan<0, 5>().bounds() == static_bounds<5>()));
+        CHECK((av.subspan<0, 5>().length() == 5));
+        CHECK(av.subspan(0, 5).length() == 5);
+        CHECK_THROWS_AS(av.subspan(0, 6).length(), fail_fast);
+        CHECK_THROWS_AS(av.subspan(1, 5).length(), fail_fast);
+    }
+
+    {
+        multi_span<int, 5> av = arr;
+        CHECK((av.subspan<5, 0>().bounds() == static_bounds<0>()));
+        CHECK((av.subspan<5, 0>().length() == 0));
+        CHECK(av.subspan(5, 0).length() == 0);
+        CHECK_THROWS_AS(av.subspan(6, 0).length(), fail_fast);
+    }
+
+    {
+        multi_span<int, dynamic_range> av;
+        CHECK((av.subspan<0, 0>().bounds() == static_bounds<0>()));
+        CHECK((av.subspan<0, 0>().length() == 0));
+        CHECK(av.subspan(0, 0).length() == 0);
+        CHECK_THROWS_AS((av.subspan<1, 0>().length()), fail_fast);
+    }
+
+    {
+        multi_span<int> av;
+        CHECK(av.subspan(0).length() == 0);
+        CHECK_THROWS_AS(av.subspan(1).length(), fail_fast);
+    }
+
+    {
+        multi_span<int> av = arr;
+        CHECK(av.subspan(0).length() == 5);
+        CHECK(av.subspan(1).length() == 4);
+        CHECK(av.subspan(4).length() == 1);
+        CHECK(av.subspan(5).length() == 0);
+        CHECK_THROWS_AS(av.subspan(6).length(), fail_fast);
+        auto av2 = av.subspan(1);
+        for (int i = 0; i < 4; ++i) CHECK(av2[i] == i + 2);
+    }
+
+    {
+        multi_span<int, 5> av = arr;
+        CHECK(av.subspan(0).length() == 5);
+        CHECK(av.subspan(1).length() == 4);
+        CHECK(av.subspan(4).length() == 1);
+        CHECK(av.subspan(5).length() == 0);
+        CHECK_THROWS_AS(av.subspan(6).length(), fail_fast);
+        auto av2 = av.subspan(1);
+        for (int i = 0; i < 4; ++i) CHECK(av2[i] == i + 2);
+    }
+}
+
+TEST_CASE("rank")
+{
+    int arr[2] = {1, 2};
+
+    {
+        multi_span<int> s;
+        CHECK(s.rank() == 1);
+    }
+
+    {
+        multi_span<int, 2> s = arr;
+        CHECK(s.rank() == 1);
+    }
+
+    int arr2d[1][1] = {};
+    {
+        multi_span<int, 1, 1> s = arr2d;
+        CHECK(s.rank() == 2);
+    }
+}
+
+TEST_CASE("extent")
+{
+    {
+        multi_span<int> s;
+        CHECK(s.extent() == 0);
+        CHECK(s.extent(0) == 0);
+        CHECK_THROWS_AS(s.extent(1), fail_fast);
+#ifdef CONFIRM_COMPILATION_ERRORS
+        CHECK(s.extent<1>() == 0);
+#endif
+    }
+
+    {
+        multi_span<int, 0> s;
+        CHECK(s.extent() == 0);
+        CHECK(s.extent(0) == 0);
+        CHECK_THROWS_AS(s.extent(1), fail_fast);
+    }
+
+    {
+        int arr2d[1][2] = {};
+
+        multi_span<int, 1, 2> s = arr2d;
+        CHECK(s.extent() == 1);
+        CHECK(s.extent<0>() == 1);
+        CHECK(s.extent<1>() == 2);
+        CHECK(s.extent(0) == 1);
+        CHECK(s.extent(1) == 2);
+        CHECK_THROWS_AS(s.extent(3), fail_fast);
+    }
+
+    {
+        int arr2d[1][2] = {};
+
+        multi_span<int, 0, 2> s = arr2d;
+        CHECK(s.extent() == 0);
+        CHECK(s.extent<0>() == 0);
+        CHECK(s.extent<1>() == 2);
+        CHECK(s.extent(0) == 0);
+        CHECK(s.extent(1) == 2);
+        CHECK_THROWS_AS(s.extent(3), fail_fast);
+    }
+}
+
+TEST_CASE("operator_function_call")
+{
+    int arr[4] = {1, 2, 3, 4};
+
+    {
+        multi_span<int> s = arr;
+        CHECK(s(0) == 1);
+        CHECK_THROWS_AS(s(5), fail_fast);
+    }
+
+    int arr2d[2][3] = {1, 2, 3, 4, 5, 6};
+
+    {
+        multi_span<int, 2, 3> s = arr2d;
+        CHECK(s(0, 0) == 1);
+        CHECK(s(0, 1) == 2);
+        CHECK(s(1, 2) == 6);
+    }
+
+    int arr3d[2][2][2] = {1, 2, 3, 4, 5, 6, 7, 8};
+
+    {
+        multi_span<int, 2, 2, 2> s = arr3d;
+        CHECK(s(0, 0, 0) == 1);
+        CHECK(s(1, 1, 1) == 8);
+    }
+}
+
+TEST_CASE("comparison_operators")
+{
+    {
+        int arr[10][2];
+        auto s1 = as_multi_span(arr);
+        multi_span<const int, dynamic_range, 2> s2 = s1;
+
+        CHECK(s1 == s2);
+
+        multi_span<int, 20> s3 = as_multi_span(s1, dim(20));
+        CHECK((s3 == s2 && s3 == s1));
+    }
+
+    {
+        multi_span<int> s1 = nullptr;
+        multi_span<int> s2 = nullptr;
+        CHECK(s1 == s2);
+        CHECK(!(s1 != s2));
+        CHECK(!(s1 < s2));
+        CHECK(s1 <= s2);
+        CHECK(!(s1 > s2));
+        CHECK(s1 >= s2);
+        CHECK(s2 == s1);
+        CHECK(!(s2 != s1));
+        CHECK(!(s2 < s1));
+        CHECK(s2 <= s1);
+        CHECK(!(s2 > s1));
+        CHECK(s2 >= s1);
+    }
+
+    {
+        int arr[] = {2, 1}; // bigger
+
+        multi_span<int> s1 = nullptr;
+        multi_span<int> s2 = arr;
+
+        CHECK(s1 != s2);
+        CHECK(s2 != s1);
+        CHECK(!(s1 == s2));
+        CHECK(!(s2 == s1));
+        CHECK(s1 < s2);
+        CHECK(!(s2 < s1));
+        CHECK(s1 <= s2);
+        CHECK(!(s2 <= s1));
+        CHECK(s2 > s1);
+        CHECK(!(s1 > s2));
+        CHECK(s2 >= s1);
+        CHECK(!(s1 >= s2));
+    }
+
+    {
+        int arr1[] = {1, 2};
+        int arr2[] = {1, 2};
+        multi_span<int> s1 = arr1;
+        multi_span<int> s2 = arr2;
+
+        CHECK(s1 == s2);
+        CHECK(!(s1 != s2));
+        CHECK(!(s1 < s2));
+        CHECK(s1 <= s2);
+        CHECK(!(s1 > s2));
+        CHECK(s1 >= s2);
+        CHECK(s2 == s1);
+        CHECK(!(s2 != s1));
+        CHECK(!(s2 < s1));
+        CHECK(s2 <= s1);
+        CHECK(!(s2 > s1));
+        CHECK(s2 >= s1);
+    }
+
+    {
+        int arr[] = {1, 2, 3};
+
+        multi_span<int> s1 = {&arr[0], 2}; // shorter
+        multi_span<int> s2 = arr;          // longer
+
+        CHECK(s1 != s2);
+        CHECK(s2 != s1);
+        CHECK(!(s1 == s2));
+        CHECK(!(s2 == s1));
+        CHECK(s1 < s2);
+        CHECK(!(s2 < s1));
+        CHECK(s1 <= s2);
+        CHECK(!(s2 <= s1));
+        CHECK(s2 > s1);
+        CHECK(!(s1 > s2));
+        CHECK(s2 >= s1);
+        CHECK(!(s1 >= s2));
+    }
+
+    {
+        int arr1[] = {1, 2}; // smaller
+        int arr2[] = {2, 1}; // bigger
+
+        multi_span<int> s1 = arr1;
+        multi_span<int> s2 = arr2;
+
+        CHECK(s1 != s2);
+        CHECK(s2 != s1);
+        CHECK(!(s1 == s2));
+        CHECK(!(s2 == s1));
+        CHECK(s1 < s2);
+        CHECK(!(s2 < s1));
+        CHECK(s1 <= s2);
+        CHECK(!(s2 <= s1));
+        CHECK(s2 > s1);
+        CHECK(!(s1 > s2));
+        CHECK(s2 >= s1);
+        CHECK(!(s1 >= s2));
+    }
+}
+
+TEST_CASE("basics")
+{
+    auto ptr = as_multi_span(new int[10], 10);
+    fill(ptr.begin(), ptr.end(), 99);
+    for (int num : ptr) {
+        CHECK(num == 99);
+    }
+
+    delete[] ptr.data();
+}
+
+TEST_CASE("bounds_checks")
+{
+    int arr[10][2];
+    auto av = as_multi_span(arr);
+
+    fill(begin(av), end(av), 0);
+
+    av[2][0] = 1;
+    av[1][1] = 3;
+
+    // out of bounds
+    CHECK_THROWS_AS(av[1][3] = 3, fail_fast);
+    CHECK_THROWS_AS((av[{1, 3}] = 3), fail_fast);
+
+    CHECK_THROWS_AS(av[10][2], fail_fast);
+    CHECK_THROWS_AS((av[{10, 2}]), fail_fast);
+
+    CHECK_THROWS_AS(av[-1][0], fail_fast);
+    CHECK_THROWS_AS((av[{-1, 0}]), fail_fast);
+
+    CHECK_THROWS_AS(av[0][-1], fail_fast);
+    CHECK_THROWS_AS((av[{0, -1}]), fail_fast);
+}
+
+void overloaded_func(multi_span<const int, dynamic_range, 3, 5> exp, int expected_value)
+{
+    for (auto val : exp) {
+        CHECK(val == expected_value);
+    }
+}
+
+void overloaded_func(multi_span<const char, dynamic_range, 3, 5> exp, char expected_value)
+{
+    for (auto val : exp) {
+        CHECK(val == expected_value);
+    }
+}
+
+void fixed_func(multi_span<int, 3, 3, 5> exp, int expected_value)
+{
+    for (auto val : exp) {
+        CHECK(val == expected_value);
+    }
+}
+
+TEST_CASE("span_parameter_test")
+{
+    auto data = new int[4][3][5];
+
+    auto av = as_multi_span(data, 4);
+
+    CHECK(av.size() == 60);
+
+    fill(av.begin(), av.end(), 34);
+
+    int count = 0;
+    for_each(av.rbegin(), av.rend(), [&](int val) { count += val; });
+    CHECK(count == 34 * 60);
+    overloaded_func(av, 34);
+
+    overloaded_func(as_multi_span(av, dim(4), dim(3), dim(5)), 34);
+
+    // fixed_func(av, 34);
+    delete[] data;
+}
+
+TEST_CASE("md_access")
+{
+    auto width = 5, height = 20;
+
+    auto imgSize = width * height;
+    auto image_ptr = new int[static_cast<std::size_t>(imgSize)][3];
+
+    // size check will be done
+    auto image_view =
+        as_multi_span(as_multi_span(image_ptr, imgSize), dim(height), dim(width), dim<3>());
+
+    iota(image_view.begin(), image_view.end(), 1);
+
+    int expected = 0;
+    for (auto i = 0; i < height; i++) {
+        for (auto j = 0; j < width; j++) {
+            CHECK(expected + 1 == image_view[i][j][0]);
+            CHECK(expected + 2 == image_view[i][j][1]);
+            CHECK(expected + 3 == image_view[i][j][2]);
+
+            auto val = image_view[{i, j, 0}];
+            CHECK(expected + 1 == val);
+            val = image_view[{i, j, 1}];
+            CHECK(expected + 2 == val);
+            val = image_view[{i, j, 2}];
+            CHECK(expected + 3 == val);
+
+            expected += 3;
+        }
+    }
+}
+
+TEST_CASE("as_multi_span")
+{
+    {
+        int* arr = new int[150];
+
+        auto av = as_multi_span(arr, dim<10>(), dim(3), dim<5>());
+
+        fill(av.begin(), av.end(), 24);
+        overloaded_func(av, 24);
+
+        delete[] arr;
+
+        array<int, 15> stdarr{0};
+        auto av2 = as_multi_span(stdarr);
+        overloaded_func(as_multi_span(av2, dim(1), dim<3>(), dim<5>()), 0);
+
+        string str = "ttttttttttttttt"; // size = 15
+        auto t = str.data();
+        (void) t;
+        auto av3 = as_multi_span(str);
+        overloaded_func(as_multi_span(av3, dim(1), dim<3>(), dim<5>()), 't');
+    }
+
+    {
+        string str;
+        multi_span<char> strspan = as_multi_span(str);
+        (void) strspan;
+        const string cstr;
+        multi_span<const char> cstrspan = as_multi_span(cstr);
+        (void) cstrspan;
+    }
+
+    {
+        int a[3][4][5];
+        auto av = as_multi_span(a);
+        const int(*b)[4][5];
+        b = a;
+        auto bv = as_multi_span(b, 3);
+
+        CHECK(av == bv);
+
+        const std::array<double, 3> arr = {0.0, 0.0, 0.0};
+        auto cv = as_multi_span(arr);
+        (void) cv;
+
+        vector<float> vec(3);
+        auto dv = as_multi_span(vec);
+        (void) dv;
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+        auto dv2 = as_multi_span(std::move(vec));
+#endif
+    }
+}
+
+TEST_CASE("empty_spans")
+{
+    {
+        multi_span<int, 0> empty_av(nullptr);
+
+        CHECK(empty_av.bounds().index_bounds() == multi_span_index<1>{0});
+        CHECK_THROWS_AS(empty_av[0], fail_fast);
+        CHECK_THROWS_AS(empty_av.begin()[0], fail_fast);
+        CHECK_THROWS_AS(empty_av.cbegin()[0], fail_fast);
+        for (auto& v : empty_av) {
+            (void) v;
+            CHECK(false);
+        }
+    }
+
+    {
+        multi_span<int> empty_av = {};
+        CHECK(empty_av.bounds().index_bounds() == multi_span_index<1>{0});
+        CHECK_THROWS_AS(empty_av[0], fail_fast);
+        CHECK_THROWS_AS(empty_av.begin()[0], fail_fast);
+        CHECK_THROWS_AS(empty_av.cbegin()[0], fail_fast);
+        for (auto& v : empty_av) {
+            (void) v;
+            CHECK(false);
+        }
+    }
+}
+
+TEST_CASE("index_constructor")
+{
+    auto arr = new int[8];
+    for (int i = 0; i < 4; ++i) {
+        arr[2 * i] = 4 + i;
+        arr[2 * i + 1] = i;
+    }
+
+    multi_span<int, dynamic_range> av(arr, 8);
+
+    ptrdiff_t a[1] = {0};
+    multi_span_index<1> i = a;
+
+    CHECK(av[i] == 4);
+
+    auto av2 = as_multi_span(av, dim<4>(), dim(2));
+    ptrdiff_t a2[2] = {0, 1};
+    multi_span_index<2> i2 = a2;
+
+    CHECK(av2[i2] == 0);
+    CHECK(av2[0][i] == 4);
+
+    delete[] arr;
+}
+
+TEST_CASE("index_constructors")
+{
+    {
+        // components of the same type
+        multi_span_index<3> i1(0, 1, 2);
+        CHECK(i1[0] == 0);
+
+        // components of different types
+        std::size_t c0 = 0;
+        std::size_t c1 = 1;
+        multi_span_index<3> i2(c0, c1, 2);
+        CHECK(i2[0] == 0);
+
+        // from array
+        multi_span_index<3> i3 = {0, 1, 2};
+        CHECK(i3[0] == 0);
+
+        // from other index of the same size type
+        multi_span_index<3> i4 = i3;
+        CHECK(i4[0] == 0);
+
+        // default
+        multi_span_index<3> i7;
+        CHECK(i7[0] == 0);
+
+        // default
+        multi_span_index<3> i9 = {};
+        CHECK(i9[0] == 0);
+    }
+
+    {
+        // components of the same type
+        multi_span_index<1> i1(0);
+        CHECK(i1[0] == 0);
+
+        // components of different types
+        std::size_t c0 = 0;
+        multi_span_index<1> i2(c0);
+        CHECK(i2[0] == 0);
+
+        // from array
+        multi_span_index<1> i3 = {0};
+        CHECK(i3[0] == 0);
+
+        // from int
+        multi_span_index<1> i4 = 0;
+        CHECK(i4[0] == 0);
+
+        // from other index of the same size type
+        multi_span_index<1> i5 = i3;
+        CHECK(i5[0] == 0);
+
+        // default
+        multi_span_index<1> i8;
+        CHECK(i8[0] == 0);
+
+        // default
+        multi_span_index<1> i9 = {};
+        CHECK(i9[0] == 0);
+    }
+
+    #ifdef CONFIRM_COMPILATION_ERRORS
+    {
+    multi_span_index<3> i1(0, 1);
+    multi_span_index<3> i2(0, 1, 2, 3);
+    multi_span_index<3> i3 = {0};
+    multi_span_index<3> i4 = {0, 1, 2, 3};
+    multi_span_index<1> i5 = {0, 1};
+    }
+    #endif
+}
+
+TEST_CASE("index_operations")
+{
+    ptrdiff_t a[3] = {0, 1, 2};
+    ptrdiff_t b[3] = {3, 4, 5};
+    multi_span_index<3> i = a;
+    multi_span_index<3> j = b;
+
+    CHECK(i[0] == 0);
+    CHECK(i[1] == 1);
+    CHECK(i[2] == 2);
+
+    {
+        multi_span_index<3> k = i + j;
+
+        CHECK(i[0] == 0);
+        CHECK(i[1] == 1);
+        CHECK(i[2] == 2);
+        CHECK(k[0] == 3);
+        CHECK(k[1] == 5);
+        CHECK(k[2] == 7);
+    }
+
+    {
+        multi_span_index<3> k = i * 3;
+
+        CHECK(i[0] == 0);
+        CHECK(i[1] == 1);
+        CHECK(i[2] == 2);
+        CHECK(k[0] == 0);
+        CHECK(k[1] == 3);
+        CHECK(k[2] == 6);
+    }
+
+    {
+        multi_span_index<3> k = 3 * i;
+
+        CHECK(i[0] == 0);
+        CHECK(i[1] == 1);
+        CHECK(i[2] == 2);
+        CHECK(k[0] == 0);
+        CHECK(k[1] == 3);
+        CHECK(k[2] == 6);
+    }
+
+    {
+        multi_span_index<2> k = details::shift_left(i);
+
+        CHECK(i[0] == 0);
+        CHECK(i[1] == 1);
+        CHECK(i[2] == 2);
+        CHECK(k[0] == 1);
+        CHECK(k[1] == 2);
+    }
+}
+
+void iterate_second_column(multi_span<int, dynamic_range, dynamic_range> av)
+{
+    auto length = av.size() / 2;
+
+    // view to the second column
+    auto section = av.section({0, 1}, {length, 1});
+
+    CHECK(section.size() == length);
+    for (auto i = 0; i < section.size(); ++i) {
+        CHECK(section[i][0] == av[i][1]);
+    }
+
+    for (auto i = 0; i < section.size(); ++i) {
+        auto idx = multi_span_index<2>{i, 0}; // avoid braces inside the CHECK macro
+        CHECK(section[idx] == av[i][1]);
+    }
+
+    CHECK(section.bounds().index_bounds()[0] == length);
+    CHECK(section.bounds().index_bounds()[1] == 1);
+    for (auto i = 0; i < section.bounds().index_bounds()[0]; ++i) {
+        for (auto j = 0; j < section.bounds().index_bounds()[1]; ++j) {
+            auto idx = multi_span_index<2>{i, j}; // avoid braces inside the CHECK macro
+            CHECK(section[idx] == av[i][1]);
+        }
+    }
+
+    auto check_sum = 0;
+    for (auto i = 0; i < length; ++i) {
+        check_sum += av[i][1];
+    }
+
+    {
+        auto idx = 0;
+        auto sum = 0;
+        for (auto num : section) {
+            CHECK(num == av[idx][1]);
+            sum += num;
+            idx++;
+        }
+
+        CHECK(sum == check_sum);
+    }
+    {
+        auto idx = length - 1;
+        auto sum = 0;
+        for (auto iter = section.rbegin(); iter != section.rend(); ++iter) {
+            CHECK(*iter == av[idx][1]);
+            sum += *iter;
+            idx--;
+        }
+
+        CHECK(sum == check_sum);
+    }
+}
+
+TEST_CASE("span_section_iteration")
+{
+    int arr[4][2] = {{4, 0}, {5, 1}, {6, 2}, {7, 3}};
+
+    // static bounds
+    {
+        multi_span<int, 4, 2> av = arr;
+        iterate_second_column(av);
+    }
+    // first bound is dynamic
+    {
+        multi_span<int, dynamic_range, 2> av = arr;
+        iterate_second_column(av);
+    }
+    // second bound is dynamic
+    {
+        multi_span<int, 4, dynamic_range> av = arr;
+        iterate_second_column(av);
+    }
+    // both bounds are dynamic
+    {
+        multi_span<int, dynamic_range, dynamic_range> av = arr;
+        iterate_second_column(av);
+    }
+}
+
+TEST_CASE("dynamic_span_section_iteration")
+{
+    auto height = 4, width = 2;
+    auto size = height * width;
+
+    auto arr = new int[static_cast<std::size_t>(size)];
+    for (auto i = 0; i < size; ++i) {
+        arr[i] = i;
+    }
+
+    auto av = as_multi_span(arr, size);
+
+    // first bound is dynamic
+    {
+        multi_span<int, dynamic_range, 2> av2 = as_multi_span(av, dim(height), dim(width));
+        iterate_second_column(av2);
+    }
+    // second bound is dynamic
+    {
+        multi_span<int, 4, dynamic_range> av2 = as_multi_span(av, dim(height), dim(width));
+        iterate_second_column(av2);
+    }
+    // both bounds are dynamic
+    {
+        multi_span<int, dynamic_range, dynamic_range> av2 =
+            as_multi_span(av, dim(height), dim(width));
+        iterate_second_column(av2);
+    }
+
+    delete[] arr;
+}
+
+TEST_CASE("span_structure_size")
+{
+    double(*arr)[3][4] = new double[100][3][4];
+    multi_span<double, dynamic_range, 3, 4> av1(arr, 10);
+
+    struct EffectiveStructure
+    {
+        double* v1;
+        ptrdiff_t v2;
+    };
+    CHECK(sizeof(av1) == sizeof(EffectiveStructure));
+
+    CHECK_THROWS_AS(av1[10][3][4], fail_fast);
+
+    multi_span<const double, dynamic_range, 6, 4> av2 =
+        as_multi_span(av1, dim(5), dim<6>(), dim<4>());
+    (void) av2;
+}
+
+TEST_CASE("fixed_size_conversions")
+{
+    int arr[] = {1, 2, 3, 4};
+
+    // converting to an multi_span from an equal size array is ok
+    multi_span<int, 4> av4 = arr;
+    CHECK(av4.length() == 4);
+
+    // converting to dynamic_range a_v is always ok
+    {
+        multi_span<int, dynamic_range> av = av4;
+        (void) av;
+    }
+    {
+        multi_span<int, dynamic_range> av = arr;
+        (void) av;
+    }
+
+// initialization or assignment to static multi_span that REDUCES size is NOT ok
+#ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        multi_span<int, 2> av2 = arr;
+    }
+    {
+        multi_span<int, 2> av2 = av4;
+    }
+#endif
+
+    {
+        multi_span<int, dynamic_range> av = arr;
+        multi_span<int, 2> av2 = av;
+        (void) av2;
+    }
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        multi_span<int, dynamic_range> av = arr;
+        multi_span<int, 2, 1> av2 = av.as_multi_span(dim<2>(), dim<2>());
+    }
+#endif
+
+    {
+        multi_span<int, dynamic_range> av = arr;
+        multi_span<int, 2, 1> av2 = as_multi_span(av, dim(2), dim(2));
+        auto workaround_macro = [&]() { return av2[{1, 0}] == 2; };
+        CHECK(workaround_macro());
+    }
+
+    // but doing so explicitly is ok
+
+    // you can convert statically
+    {
+        multi_span<int, 2> av2 = {arr, 2};
+        (void) av2;
+    }
+    {
+        multi_span<int, 1> av2 = av4.first<1>();
+        (void) av2;
+    }
+
+    // ...or dynamically
+    {
+        // NB: implicit conversion to multi_span<int,2> from multi_span<int,dynamic_range>
+        multi_span<int, 1> av2 = av4.first(1);
+        (void) av2;
+    }
+
+    // initialization or assignment to static multi_span that requires size INCREASE is not ok.
+    int arr2[2] = {1, 2};
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        multi_span<int, 4> av4 = arr2;
+    }
+    {
+        multi_span<int, 2> av2 = arr2;
+        multi_span<int, 4> av4 = av2;
+    }
+#endif
+    {
+        auto f = [&]() {
+            multi_span<int, 4> av9 = {arr2, 2};
+            (void) av9;
+        };
+        CHECK_THROWS_AS(f(), fail_fast);
+    }
+
+    // this should fail - we are trying to assign a small dynamic a_v to a fixed_size larger one
+    multi_span<int, dynamic_range> av = arr2;
+    auto f = [&]() {
+        multi_span<int, 4> av2 = av;
+        (void) av2;
+    };
+    CHECK_THROWS_AS(f(), fail_fast);
+}
+
+TEST_CASE("as_writeable_bytes")
+{
+    int a[] = {1, 2, 3, 4};
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        // you should not be able to get writeable bytes for const objects
+        multi_span<const int, dynamic_range> av = a;
+        auto wav = av.as_writeable_bytes();
+#endif
+    }
+
+    {
+        multi_span<int, dynamic_range> av;
+        auto wav = as_writeable_bytes(av);
+        CHECK(wav.length() == av.length());
+        CHECK(wav.length() == 0);
+        CHECK(wav.size_bytes() == 0);
+    }
+
+    {
+        multi_span<int, dynamic_range> av = a;
+        auto wav = as_writeable_bytes(av);
+        CHECK(wav.data() == reinterpret_cast<byte*>(&a[0]));
+        CHECK(static_cast<std::size_t>(wav.length()) == sizeof(a));
+    }
+}
+
+TEST_CASE("iterator")
+{
+    int a[] = {1, 2, 3, 4};
+
+    {
+        multi_span<int, dynamic_range> av = a;
+        auto wav = as_writeable_bytes(av);
+        for (auto& b : wav) {
+            b = byte(0);
+        }
+        for (std::size_t i = 0; i < 4; ++i) {
+            CHECK(a[i] == 0);
+        }
+    }
+
+    {
+        multi_span<int, dynamic_range> av = a;
+        for (auto& n : av) {
+            n = 1;
+        }
+        for (std::size_t i = 0; i < 4; ++i) {
+            CHECK(a[i] == 1);
+        }
+    }
+}
diff --git a/tests/no_exception_ensure_tests.cpp b/tests/no_exception_ensure_tests.cpp
new file mode 100644
index 0000000..5da021e
--- /dev/null
+++ b/tests/no_exception_ensure_tests.cpp
@@ -0,0 +1,53 @@
+///////////////////////////////////////////////////////////////////////////////

+//

+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.

+//

+// This code is licensed under the MIT License (MIT).

+//

+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

+// THE SOFTWARE.

+//

+///////////////////////////////////////////////////////////////////////////////

+

+#include <cstdlib>      // for std::exit

+#include <gsl/span>     // for span

+

+int operator_subscript_no_throw()

+{

+    int arr[10]; 

+    gsl::span<int> sp { arr };

+    return sp[11];

+}

+

+

+void test_terminate()

+{ 

+    std::exit(0);

+}

+

+void setup_termination_handler()

+{

+#if defined(_MSC_VER)

+

+    auto& handler = gsl::details::get_terminate_handler();

+    handler = &test_terminate;

+

+#else

+

+    std::set_terminate(test_terminate);

+

+#endif

+}

+

+

+int main()

+{

+    setup_termination_handler();

+    operator_subscript_no_throw();

+    return -1;

+}

diff --git a/tests/no_exception_throw_tests.cpp b/tests/no_exception_throw_tests.cpp
new file mode 100644
index 0000000..dd4e994
--- /dev/null
+++ b/tests/no_exception_throw_tests.cpp
@@ -0,0 +1,51 @@
+///////////////////////////////////////////////////////////////////////////////

+//

+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.

+//

+// This code is licensed under the MIT License (MIT).

+//

+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

+// THE SOFTWARE.

+//

+///////////////////////////////////////////////////////////////////////////////

+

+#include <cstdlib>      // for std::exit

+#include <gsl/gsl_util> // for narrow

+

+int narrow_no_throw()

+{

+    long long bigNumber = 0x0fffffffffffffff;

+    return gsl::narrow<int>(bigNumber); 

+}

+

+void test_terminate()

+{ 

+    std::exit(0);

+}

+

+void setup_termination_handler()

+{

+#if defined(_MSC_VER)

+

+    auto& handler = gsl::details::get_terminate_handler();

+    handler = &test_terminate;

+

+#else

+

+    std::set_terminate(test_terminate);

+

+#endif

+}

+

+

+int main()

+{

+    setup_termination_handler();

+    narrow_no_throw();

+    return -1;

+}

diff --git a/tests/notnull_tests.cpp b/tests/notnull_tests.cpp
new file mode 100644
index 0000000..1cb9c10
--- /dev/null
+++ b/tests/notnull_tests.cpp
@@ -0,0 +1,390 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <catch/catch.hpp> // for AssertionHandler, StringRef, CHECK, TEST_...
+
+#include <gsl/pointers> // for not_null, operator<, operator<=, operator>
+
+#include <algorithm> // for addressof
+#include <memory>    // for shared_ptr, make_shared, operator<, opera...
+#include <sstream>   // for operator<<, ostringstream, basic_ostream:...
+#include <stdint.h>  // for uint16_t
+#include <string>    // for basic_string, operator==, string, operator<<
+#include <typeinfo>  // for type_info
+
+namespace gsl {
+struct fail_fast;
+}  // namespace gsl
+
+using namespace gsl;
+
+struct MyBase
+{
+};
+struct MyDerived : public MyBase
+{
+};
+struct Unrelated
+{
+};
+
+// stand-in for a user-defined ref-counted class
+template <typename T>
+struct RefCounted
+{
+    RefCounted(T* p) : p_(p) {}
+    operator T*() { return p_; }
+    T* p_;
+};
+
+// user defined smart pointer with comparison operators returning non bool value
+template <typename T>
+struct CustomPtr
+{
+    CustomPtr(T* p) : p_(p) {}
+    operator T*() { return p_; }
+    bool operator!=(std::nullptr_t) const { return p_ != nullptr; }
+    T* p_ = nullptr;
+};
+
+template <typename T, typename U>
+std::string operator==(CustomPtr<T> const& lhs, CustomPtr<U> const& rhs)
+{
+    return reinterpret_cast<const void*>(lhs.p_) == reinterpret_cast<const void*>(rhs.p_) ? "true"
+                                                                                          : "false";
+}
+
+template <typename T, typename U>
+std::string operator!=(CustomPtr<T> const& lhs, CustomPtr<U> const& rhs)
+{
+    return reinterpret_cast<const void*>(lhs.p_) != reinterpret_cast<const void*>(rhs.p_) ? "true"
+                                                                                          : "false";
+}
+
+template <typename T, typename U>
+std::string operator<(CustomPtr<T> const& lhs, CustomPtr<U> const& rhs)
+{
+    return reinterpret_cast<const void*>(lhs.p_) < reinterpret_cast<const void*>(rhs.p_) ? "true"
+                                                                                         : "false";
+}
+
+template <typename T, typename U>
+std::string operator>(CustomPtr<T> const& lhs, CustomPtr<U> const& rhs)
+{
+    return reinterpret_cast<const void*>(lhs.p_) > reinterpret_cast<const void*>(rhs.p_) ? "true"
+                                                                                         : "false";
+}
+
+template <typename T, typename U>
+std::string operator<=(CustomPtr<T> const& lhs, CustomPtr<U> const& rhs)
+{
+    return reinterpret_cast<const void*>(lhs.p_) <= reinterpret_cast<const void*>(rhs.p_) ? "true"
+                                                                                          : "false";
+}
+
+template <typename T, typename U>
+std::string operator>=(CustomPtr<T> const& lhs, CustomPtr<U> const& rhs)
+{
+    return reinterpret_cast<const void*>(lhs.p_) >= reinterpret_cast<const void*>(rhs.p_) ? "true"
+                                                                                          : "false";
+}
+
+struct NonCopyableNonMovable
+{
+    NonCopyableNonMovable() = default;
+    NonCopyableNonMovable(const NonCopyableNonMovable&) = delete;
+    NonCopyableNonMovable& operator=(const NonCopyableNonMovable&) = delete;
+    NonCopyableNonMovable(NonCopyableNonMovable&&) = delete;
+    NonCopyableNonMovable& operator=(NonCopyableNonMovable&&) = delete;
+};
+
+bool helper(not_null<int*> p) { return *p == 12; }
+bool helper_const(not_null<const int*> p) { return *p == 12; }
+
+TEST_CASE("TestNotNullConstructors")
+{
+#ifdef CONFIRM_COMPILATION_ERRORS
+    not_null<int*> p = nullptr;         // yay...does not compile!
+    not_null<std::vector<char>*> p = 0; // yay...does not compile!
+    not_null<int*> p;                   // yay...does not compile!
+    std::unique_ptr<int> up = std::make_unique<int>(120);
+    not_null<int*> p = up;
+
+    // Forbid non-nullptr assignable types
+    not_null<std::vector<int>> f(std::vector<int>{1});
+    not_null<int> z(10);
+    not_null<std::vector<int>> y({1, 2});
+#endif
+    int i = 12;
+    auto rp = RefCounted<int>(&i);
+    not_null<int*> p(rp);
+    CHECK(p.get() == &i);
+
+    not_null<std::shared_ptr<int>> x(
+        std::make_shared<int>(10)); // shared_ptr<int> is nullptr assignable
+
+#ifdef GSL_THROW_ON_CONTRACT_VIOLATION
+    int* pi = nullptr;
+    CHECK_THROWS_AS(not_null<decltype(pi)>(pi), fail_fast);
+#endif    
+}
+
+template<typename T>
+void ostream_helper(T v)
+{
+    not_null<T*> p(&v);
+    {
+        std::ostringstream os;
+        std::ostringstream ref;
+        os << p;
+        ref << &v;
+        CHECK(os.str() == ref.str());
+    }
+    {
+        std::ostringstream os;
+        std::ostringstream ref;
+        os << *p;
+        ref << v;
+        CHECK(os.str() == ref.str());
+    }
+}
+
+TEST_CASE("TestNotNullostream")
+{
+    ostream_helper<int>(17);
+    ostream_helper<float>(21.5f);
+    ostream_helper<double>(3.4566e-7f);
+    ostream_helper<char>('c');
+    ostream_helper<uint16_t>(0x0123u);
+    ostream_helper<const char*>("cstring");
+    ostream_helper<std::string>("string");
+}
+
+
+TEST_CASE("TestNotNullCasting")
+{
+    MyBase base;
+    MyDerived derived;
+    Unrelated unrelated;
+    not_null<Unrelated*> u{&unrelated};
+    (void) u;
+    not_null<MyDerived*> p{&derived};
+    not_null<MyBase*> q(&base);
+    q = p; // allowed with heterogeneous copy ctor
+    CHECK(q == p);
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+    q = u; // no viable conversion possible between MyBase* and Unrelated*
+    p = q; // not possible to implicitly convert MyBase* to MyDerived*
+
+    not_null<Unrelated*> r = p;
+    not_null<Unrelated*> s = reinterpret_cast<Unrelated*>(p);
+#endif
+    not_null<Unrelated*> t(reinterpret_cast<Unrelated*>(p.get()));
+    CHECK(reinterpret_cast<void*>(p.get()) == reinterpret_cast<void*>(t.get()));
+}
+
+TEST_CASE("TestNotNullAssignment")
+{
+    int i = 12;
+    not_null<int*> p(&i);
+    CHECK(helper(p));
+
+    int* q = nullptr;
+    CHECK_THROWS_AS(p = not_null<int*>(q), fail_fast);
+}
+
+TEST_CASE("TestNotNullRawPointerComparison")
+{
+    int ints[2] = {42, 43};
+    int* p1 = &ints[0];
+    const int* p2 = &ints[1];
+
+    using NotNull1 = not_null<decltype(p1)>;
+    using NotNull2 = not_null<decltype(p2)>;
+
+    CHECK((NotNull1(p1) == NotNull1(p1)) == true);
+    CHECK((NotNull1(p1) == NotNull2(p2)) == false);
+
+    CHECK((NotNull1(p1) != NotNull1(p1)) == false);
+    CHECK((NotNull1(p1) != NotNull2(p2)) == true);
+
+    CHECK((NotNull1(p1) < NotNull1(p1)) == false);
+    CHECK((NotNull1(p1) < NotNull2(p2)) == (p1 < p2));
+    CHECK((NotNull2(p2) < NotNull1(p1)) == (p2 < p1));
+
+    CHECK((NotNull1(p1) > NotNull1(p1)) == false);
+    CHECK((NotNull1(p1) > NotNull2(p2)) == (p1 > p2));
+    CHECK((NotNull2(p2) > NotNull1(p1)) == (p2 > p1));
+
+    CHECK((NotNull1(p1) <= NotNull1(p1)) == true);
+    CHECK((NotNull1(p1) <= NotNull2(p2)) == (p1 <= p2));
+    CHECK((NotNull2(p2) <= NotNull1(p1)) == (p2 <= p1));
+
+}
+
+TEST_CASE("TestNotNullDereferenceOperator")
+{
+    {
+        auto sp1 = std::make_shared<NonCopyableNonMovable>();
+
+        using NotNullSp1 = not_null<decltype(sp1)>;
+        CHECK(typeid(*sp1) == typeid(*NotNullSp1(sp1))); 
+        CHECK(std::addressof(*NotNullSp1(sp1)) == std::addressof(*sp1));
+    }
+
+    {
+        int ints[1] = { 42 };
+        CustomPtr<int> p1(&ints[0]);
+
+        using NotNull1 = not_null<decltype(p1)>;
+        CHECK(typeid(*NotNull1(p1)) == typeid(*p1));
+        CHECK(*NotNull1(p1) == 42);
+        *NotNull1(p1) = 43;
+        CHECK(ints[0] == 43);
+    }
+
+    {
+        int v = 42;
+        gsl::not_null<int*> p(&v);
+        CHECK(typeid(*p) == typeid(*(&v)));
+        *p = 43;
+        CHECK(v == 43);
+    }
+}
+
+TEST_CASE("TestNotNullSharedPtrComparison")
+{
+    auto sp1 = std::make_shared<int>(42);
+    auto sp2 = std::make_shared<const int>(43);
+
+    using NotNullSp1 = not_null<decltype(sp1)>;
+    using NotNullSp2 = not_null<decltype(sp2)>;
+
+    CHECK((NotNullSp1(sp1) == NotNullSp1(sp1)) == true);
+    CHECK((NotNullSp1(sp1) == NotNullSp2(sp2)) == false);
+
+    CHECK((NotNullSp1(sp1) != NotNullSp1(sp1)) == false);
+    CHECK((NotNullSp1(sp1) != NotNullSp2(sp2)) == true);
+
+    CHECK((NotNullSp1(sp1) < NotNullSp1(sp1)) == false);
+    CHECK((NotNullSp1(sp1) < NotNullSp2(sp2)) == (sp1 < sp2));
+    CHECK((NotNullSp2(sp2) < NotNullSp1(sp1)) == (sp2 < sp1));
+
+    CHECK((NotNullSp1(sp1) > NotNullSp1(sp1)) == false);
+    CHECK((NotNullSp1(sp1) > NotNullSp2(sp2)) == (sp1 > sp2));
+    CHECK((NotNullSp2(sp2) > NotNullSp1(sp1)) == (sp2 > sp1));
+
+    CHECK((NotNullSp1(sp1) <= NotNullSp1(sp1)) == true);
+    CHECK((NotNullSp1(sp1) <= NotNullSp2(sp2)) == (sp1 <= sp2));
+    CHECK((NotNullSp2(sp2) <= NotNullSp1(sp1)) == (sp2 <= sp1));
+
+    CHECK((NotNullSp1(sp1) >= NotNullSp1(sp1)) == true);
+    CHECK((NotNullSp1(sp1) >= NotNullSp2(sp2)) == (sp1 >= sp2));
+    CHECK((NotNullSp2(sp2) >= NotNullSp1(sp1)) == (sp2 >= sp1));
+}
+
+TEST_CASE("TestNotNullCustomPtrComparison")
+{
+    int ints[2] = {42, 43};
+    CustomPtr<int> p1(&ints[0]);
+    CustomPtr<const int> p2(&ints[1]);
+
+    using NotNull1 = not_null<decltype(p1)>;
+    using NotNull2 = not_null<decltype(p2)>;
+
+    CHECK((NotNull1(p1) == NotNull1(p1)) == "true");
+    CHECK((NotNull1(p1) == NotNull2(p2)) == "false");
+
+    CHECK((NotNull1(p1) != NotNull1(p1)) == "false");
+    CHECK((NotNull1(p1) != NotNull2(p2)) == "true");
+
+    CHECK((NotNull1(p1) < NotNull1(p1)) == "false");
+    CHECK((NotNull1(p1) < NotNull2(p2)) == (p1 < p2));
+    CHECK((NotNull2(p2) < NotNull1(p1)) == (p2 < p1));
+
+    CHECK((NotNull1(p1) > NotNull1(p1)) == "false");
+    CHECK((NotNull1(p1) > NotNull2(p2)) == (p1 > p2));
+    CHECK((NotNull2(p2) > NotNull1(p1)) == (p2 > p1));
+
+    CHECK((NotNull1(p1) <= NotNull1(p1)) == "true");
+    CHECK((NotNull1(p1) <= NotNull2(p2)) == (p1 <= p2));
+    CHECK((NotNull2(p2) <= NotNull1(p1)) == (p2 <= p1));
+
+    CHECK((NotNull1(p1) >= NotNull1(p1)) == "true");
+    CHECK((NotNull1(p1) >= NotNull2(p2)) == (p1 >= p2));
+    CHECK((NotNull2(p2) >= NotNull1(p1)) == (p2 >= p1));
+}
+
+
+#if defined(__cplusplus) && (__cplusplus >= 201703L)
+TEST_CASE("TestNotNullConstructorTypeDeduction")
+{
+    {
+        int i = 42;
+
+        not_null x{&i};
+        helper(not_null{&i});
+        helper_const(not_null{&i});
+
+        CHECK(*x == 42);
+    }
+
+    {
+        int i = 42;
+        int* p = &i;
+
+        not_null x{p};
+        helper(not_null{p});
+        helper_const(not_null{p});
+
+        CHECK(*x == 42);
+    }
+
+    {
+        auto workaround_macro = []() {
+            int* p1 = nullptr;
+            not_null x{p1};
+        };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    }
+
+    {
+        auto workaround_macro = []() {
+            const int* p1 = nullptr;
+            not_null x{p1};
+        };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    }
+
+    {
+        int* p = nullptr;
+
+        CHECK_THROWS_AS(helper(not_null{p}), fail_fast);
+        CHECK_THROWS_AS(helper_const(not_null{p}), fail_fast);
+    }
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        not_null x{nullptr};
+        helper(not_null{nullptr});
+        helper_const(not_null{nullptr});
+    }
+#endif
+}
+#endif // #if defined(__cplusplus) && (__cplusplus >= 201703L)
+
+static_assert(std::is_nothrow_move_constructible<not_null<void *>>::value, "not_null must be no-throw move constructible");
diff --git a/tests/owner_tests.cpp b/tests/owner_tests.cpp
new file mode 100644
index 0000000..94822f5
--- /dev/null
+++ b/tests/owner_tests.cpp
@@ -0,0 +1,42 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <catch/catch.hpp> // for AssertionHandler, StringRef, CHECK, TEST_...
+
+#include <gsl/pointers> // for owner
+
+using namespace gsl;
+
+void f(int* i) { *i += 1; }
+
+TEST_CASE("basic_test")
+{
+    owner<int*> p = new int(120);
+    CHECK(*p == 120);
+    f(p);
+    CHECK(*p == 121);
+    delete p;
+}
+
+TEST_CASE("check_pointer_constraint")
+{
+    #ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        owner<int> integerTest = 10;
+        owner<std::shared_ptr<int>> sharedPtrTest(new int(10));
+    }
+    #endif
+}
diff --git a/tests/span_tests.cpp b/tests/span_tests.cpp
new file mode 100644
index 0000000..20279ec
--- /dev/null
+++ b/tests/span_tests.cpp
@@ -0,0 +1,1464 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <catch/catch.hpp> // for AssertionHandler, StringRef, CHECK, TEST_...
+
+#include <gsl/gsl_byte> // for byte
+#include <gsl/gsl_util> // for narrow_cast, at
+#include <gsl/span>     // for span, span_iterator, operator==, operator!=
+
+#include <array>       // for array
+#include <iostream>    // for ptrdiff_t
+#include <iterator>    // for reverse_iterator, operator-, operator==
+#include <memory>      // for unique_ptr, shared_ptr, make_unique, allo...
+#include <regex>       // for match_results, sub_match, match_results<>...
+#include <stddef.h>    // for ptrdiff_t
+#include <string>      // for string
+#include <type_traits> // for integral_constant<>::value, is_default_co...
+#include <vector>      // for vector
+
+namespace gsl {
+struct fail_fast;
+}  // namespace gsl
+
+using namespace std;
+using namespace gsl;
+
+namespace
+{
+struct BaseClass
+{
+};
+struct DerivedClass : BaseClass
+{
+};
+}
+
+TEST_CASE("default_constructor")
+{
+    {
+        span<int> s;
+        CHECK((s.size() == 0 && s.data() == nullptr));
+
+        span<const int> cs;
+        CHECK((cs.size() == 0 && cs.data() == nullptr));
+    }
+
+    {
+        span<int, 0> s;
+        CHECK((s.size() == 0 && s.data() == nullptr));
+
+        span<const int, 0> cs;
+        CHECK((cs.size() == 0 && cs.data() == nullptr));
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        span<int, 1> s;
+        CHECK((s.size() == 1 && s.data() == nullptr)); // explains why it can't compile
+#endif
+    }
+
+    {
+        span<int> s{};
+        CHECK((s.size() == 0 && s.data() == nullptr));
+
+        span<const int> cs{};
+        CHECK((cs.size() == 0 && cs.data() == nullptr));
+    }
+}
+
+TEST_CASE("size_optimization")
+{
+    {
+        span<int> s;
+        CHECK(sizeof(s) == sizeof(int*) + sizeof(ptrdiff_t));
+    }
+
+    {
+        span<int, 0> s;
+        CHECK(sizeof(s) == sizeof(int*));
+    }
+}
+
+TEST_CASE("from_nullptr_size_constructor")
+{
+    {
+        span<int> s{nullptr, static_cast<span<int>::index_type>(0)};
+        CHECK((s.size() == 0 && s.data() == nullptr));
+
+        span<const int> cs{nullptr, static_cast<span<int>::index_type>(0)};
+        CHECK((cs.size() == 0 && cs.data() == nullptr));
+    }
+
+    {
+        span<int, 0> s{nullptr, static_cast<span<int>::index_type>(0)};
+        CHECK((s.size() == 0 && s.data() == nullptr));
+
+        span<const int, 0> cs{nullptr, static_cast<span<int>::index_type>(0)};
+        CHECK((cs.size() == 0 && cs.data() == nullptr));
+    }
+
+    {
+        auto workaround_macro = []() {
+            span<int, 1> s{nullptr, static_cast<span<int>::index_type>(0)};
+        };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    }
+
+    {
+        auto workaround_macro = []() { span<int> s{nullptr, 1}; };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+
+        auto const_workaround_macro = []() { span<const int> cs{nullptr, 1}; };
+        CHECK_THROWS_AS(const_workaround_macro(), fail_fast);
+    }
+
+    {
+        auto workaround_macro = []() { span<int, 0> s{nullptr, 1}; };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+
+        auto const_workaround_macro = []() { span<const int, 0> s{nullptr, 1}; };
+        CHECK_THROWS_AS(const_workaround_macro(), fail_fast);
+    }
+
+    {
+        span<int*> s{nullptr, static_cast<span<int>::index_type>(0)};
+        CHECK((s.size() == 0 && s.data() == nullptr));
+
+        span<const int*> cs{nullptr, static_cast<span<int>::index_type>(0)};
+        CHECK((cs.size() == 0 && cs.data() == nullptr));
+    }
+}
+
+TEST_CASE("from_pointer_length_constructor")
+{
+    int arr[4] = {1, 2, 3, 4};
+
+    {
+        for(int i = 0; i<4 ; ++i)
+        {
+            {
+                span<int> s = { &arr[0], i };
+                CHECK(s.size() == i);
+                CHECK(s.data() == &arr[0]);
+                CHECK(s.empty() == (i == 0));
+                for (int j = 0; j < i; ++j)
+                {
+                    CHECK(arr[j] == s[j]);
+                    CHECK(arr[j] == s.at(j));
+                    CHECK(arr[j] == s(j));
+                }
+            }
+            {
+                span<int> s = { &arr[i], 4-i };
+                CHECK(s.size() == 4-i);
+                CHECK(s.data() == &arr[i]);
+                CHECK(s.empty() == (4-i == 0));
+                for (int j = 0; j < 4-i; ++j)
+                {
+                    CHECK(arr[j+i] == s[j]);
+                    CHECK(arr[j+i] == s.at(j));
+                    CHECK(arr[j+i] == s(j));
+                }
+            }
+        }
+    }
+
+    {
+        span<int, 2> s{&arr[0], 2};
+        CHECK((s.size() == 2 && s.data() == &arr[0]));
+        CHECK((s[0] == 1 && s[1] == 2));
+    }
+
+    {
+        int* p = nullptr;
+        span<int> s{p, static_cast<span<int>::index_type>(0)};
+        CHECK((s.size() == 0 && s.data() == nullptr));
+    }
+
+    {
+        int* p = nullptr;
+        auto workaround_macro = [=]() { span<int> s{p, 2}; };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    }
+
+    {
+        auto s = make_span(&arr[0], 2);
+        CHECK((s.size() == 2 && s.data() == &arr[0]));
+        CHECK((s[0] == 1 && s[1] == 2));
+    }
+
+    {
+        int* p = nullptr;
+        auto s = make_span(p, static_cast<span<int>::index_type>(0));
+        CHECK((s.size() == 0 && s.data() == nullptr));
+    }
+
+    {
+        int* p = nullptr;
+        auto workaround_macro = [=]() { make_span(p, 2); };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    }
+}
+
+TEST_CASE("from_pointer_pointer_constructor")
+{
+    int arr[4] = {1, 2, 3, 4};
+
+    {
+        span<int> s{&arr[0], &arr[2]};
+        CHECK((s.size() == 2 && s.data() == &arr[0]));
+        CHECK((s[0] == 1 && s[1] == 2));
+    }
+
+    {
+        span<int, 2> s{&arr[0], &arr[2]};
+        CHECK((s.size() == 2 && s.data() == &arr[0]));
+        CHECK((s[0] == 1 && s[1] == 2));
+    }
+
+    {
+        span<int> s{&arr[0], &arr[0]};
+        CHECK((s.size() == 0 && s.data() == &arr[0]));
+    }
+
+    {
+        span<int, 0> s{&arr[0], &arr[0]};
+        CHECK((s.size() == 0 && s.data() == &arr[0]));
+    }
+
+    // this will fail the std::distance() precondition, which asserts on MSVC debug builds
+    //{
+    //    auto workaround_macro = [&]() { span<int> s{&arr[1], &arr[0]}; };
+    //    CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    //}
+
+    // this will fail the std::distance() precondition, which asserts on MSVC debug builds
+    //{
+    //    int* p = nullptr;
+    //    auto workaround_macro = [&]() { span<int> s{&arr[0], p}; };
+    //    CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    //}
+
+    {
+        int* p = nullptr;
+        span<int> s{p, p};
+        CHECK((s.size() == 0 && s.data() == nullptr));
+    }
+
+    {
+        int* p = nullptr;
+        span<int, 0> s{p, p};
+        CHECK((s.size() == 0 && s.data() == nullptr));
+    }
+
+    // this will fail the std::distance() precondition, which asserts on MSVC debug builds
+    //{
+    //    int* p = nullptr;
+    //    auto workaround_macro = [&]() { span<int> s{&arr[0], p}; };
+    //    CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    //}
+
+    {
+        auto s = make_span(&arr[0], &arr[2]);
+        CHECK((s.size() == 2 && s.data() == &arr[0]));
+        CHECK((s[0] == 1 && s[1] == 2));
+    }
+
+    {
+        auto s = make_span(&arr[0], &arr[0]);
+        CHECK((s.size() == 0 && s.data() == &arr[0]));
+    }
+
+    {
+        int* p = nullptr;
+        auto s = make_span(p, p);
+        CHECK((s.size() == 0 && s.data() == nullptr));
+    }
+}
+
+TEST_CASE("from_array_constructor")
+{
+    int arr[5] = {1, 2, 3, 4, 5};
+
+    {
+        span<int> s{arr};
+        CHECK((s.size() == 5 && s.data() == &arr[0]));
+    }
+
+    {
+        span<int, 5> s{arr};
+        CHECK((s.size() == 5 && s.data() == &arr[0]));
+    }
+
+    int arr2d[2][3] = {1, 2, 3, 4, 5, 6};
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        span<int, 6> s{arr};
+    }
+
+    {
+        span<int, 0> s{arr};
+        CHECK((s.size() == 0 && s.data() == &arr[0]));
+    }
+
+    {
+        span<int> s{arr2d};
+        CHECK((s.size() == 6 && s.data() == &arr2d[0][0]));
+        CHECK((s[0] == 1 && s[5] == 6));
+    }
+
+    {
+        span<int, 0> s{arr2d};
+        CHECK((s.size() == 0 && s.data() == &arr2d[0][0]));
+    }
+
+    {
+        span<int, 6> s{arr2d};
+    }
+#endif
+    {
+        span<int[3]> s{&(arr2d[0]), 1};
+        CHECK((s.size() == 1 && s.data() == &arr2d[0]));
+    }
+
+    int arr3d[2][3][2] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        span<int> s{arr3d};
+        CHECK((s.size() == 12 && s.data() == &arr3d[0][0][0]));
+        CHECK((s[0] == 1 && s[11] == 12));
+    }
+
+    {
+        span<int, 0> s{arr3d};
+        CHECK((s.size() == 0 && s.data() == &arr3d[0][0][0]));
+    }
+
+    {
+        span<int, 11> s{arr3d};
+    }
+
+    {
+        span<int, 12> s{arr3d};
+        CHECK((s.size() == 12 && s.data() == &arr3d[0][0][0]));
+        CHECK((s[0] == 1 && s[5] == 6));
+    }
+#endif
+    {
+        span<int[3][2]> s{&arr3d[0], 1};
+        CHECK((s.size() == 1 && s.data() == &arr3d[0]));
+    }
+
+    {
+        auto s = make_span(arr);
+        CHECK((s.size() == 5 && s.data() == &arr[0]));
+    }
+
+    {
+        auto s = make_span(&(arr2d[0]), 1);
+        CHECK((s.size() == 1 && s.data() == &arr2d[0]));
+    }
+
+    {
+        auto s = make_span(&arr3d[0], 1);
+        CHECK((s.size() == 1 && s.data() == &arr3d[0]));
+    }
+}
+
+TEST_CASE("from_dynamic_array_constructor")
+{
+    double(*arr)[3][4] = new double[100][3][4];
+
+    {
+        span<double> s(&arr[0][0][0], 10);
+        CHECK((s.size() == 10 && s.data() == &arr[0][0][0]));
+    }
+
+    {
+        auto s = make_span(&arr[0][0][0], 10);
+        CHECK((s.size() == 10 && s.data() == &arr[0][0][0]));
+    }
+
+    delete[] arr;
+}
+
+TEST_CASE("from_std_array_constructor")
+{
+    std::array<int, 4> arr = {1, 2, 3, 4};
+
+    {
+        span<int> s{arr};
+        CHECK((s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data()));
+
+        span<const int> cs{arr};
+        CHECK((cs.size() == narrow_cast<ptrdiff_t>(arr.size()) && cs.data() == arr.data()));
+    }
+
+    {
+        span<int, 4> s{arr};
+        CHECK((s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data()));
+
+        span<const int, 4> cs{arr};
+        CHECK((cs.size() == narrow_cast<ptrdiff_t>(arr.size()) && cs.data() == arr.data()));
+    }
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        span<int, 2> s{arr};
+        CHECK((s.size() == 2 && s.data() == arr.data()));
+
+        span<const int, 2> cs{arr};
+        CHECK((cs.size() == 2 && cs.data() == arr.data()));
+    }
+
+    {
+        span<int, 0> s{arr};
+        CHECK((s.size() == 0 && s.data() == arr.data()));
+
+        span<const int, 0> cs{arr};
+        CHECK((cs.size() == 0 && cs.data() == arr.data()));
+    }
+
+    {
+        span<int, 5> s{arr};
+    }
+
+    {
+        auto get_an_array = []() -> std::array<int, 4> { return {1, 2, 3, 4}; };
+        auto take_a_span = [](span<int> s) { static_cast<void>(s); };
+        // try to take a temporary std::array
+        take_a_span(get_an_array());
+    }
+#endif
+
+    {
+        auto get_an_array = []() -> std::array<int, 4> { return {1, 2, 3, 4}; };
+        auto take_a_span = [](span<const int> s) { static_cast<void>(s); };
+        // try to take a temporary std::array
+        take_a_span(get_an_array());
+    }
+
+    {
+        auto s = make_span(arr);
+        CHECK((s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data()));
+    }
+}
+
+TEST_CASE("from_const_std_array_constructor")
+{
+    const std::array<int, 4> arr = {1, 2, 3, 4};
+
+    {
+        span<const int> s{arr};
+        CHECK((s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data()));
+    }
+
+    {
+        span<const int, 4> s{arr};
+        CHECK((s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data()));
+    }
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        span<const int, 2> s{arr};
+        CHECK((s.size() == 2 && s.data() == arr.data()));
+    }
+
+    {
+        span<const int, 0> s{arr};
+        CHECK((s.size() == 0 && s.data() == arr.data()));
+    }
+
+    {
+        span<const int, 5> s{arr};
+    }
+#endif
+
+    {
+        auto get_an_array = []() -> const std::array<int, 4> { return {1, 2, 3, 4}; };
+        auto take_a_span = [](span<const int> s) { static_cast<void>(s); };
+        // try to take a temporary std::array
+        take_a_span(get_an_array());
+    }
+
+    {
+        auto s = make_span(arr);
+        CHECK((s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data()));
+    }
+}
+
+TEST_CASE("from_std_array_const_constructor")
+{
+    std::array<const int, 4> arr = {1, 2, 3, 4};
+
+    {
+        span<const int> s{arr};
+        CHECK((s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data()));
+    }
+
+    {
+        span<const int, 4> s{arr};
+        CHECK((s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data()));
+    }
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        span<const int, 2> s{arr};
+        CHECK((s.size() == 2 && s.data() == arr.data()));
+    }
+
+    {
+        span<const int, 0> s{arr};
+        CHECK((s.size() == 0 && s.data() == arr.data()));
+    }
+
+    {
+        span<const int, 5> s{arr};
+    }
+
+    {
+        span<int, 4> s{arr};
+    }
+#endif
+
+    {
+        auto s = make_span(arr);
+        CHECK((s.size() == narrow_cast<ptrdiff_t>(arr.size()) && s.data() == arr.data()));
+    }
+}
+
+TEST_CASE("from_container_constructor")
+{
+    std::vector<int> v = {1, 2, 3};
+    const std::vector<int> cv = v;
+
+    {
+        span<int> s{v};
+        CHECK((s.size() == narrow_cast<std::ptrdiff_t>(v.size()) && s.data() == v.data()));
+
+        span<const int> cs{v};
+        CHECK((cs.size() == narrow_cast<std::ptrdiff_t>(v.size()) && cs.data() == v.data()));
+    }
+
+    std::string str = "hello";
+    const std::string cstr = "hello";
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        span<char> s{str};
+        CHECK((s.size() == narrow_cast<std::ptrdiff_t>(str.size()) && s.data() == str.data()));
+#endif
+        span<const char> cs{str};
+        CHECK((cs.size() == narrow_cast<std::ptrdiff_t>(str.size()) && cs.data() == str.data()));
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        span<char> s{cstr};
+#endif
+        span<const char> cs{cstr};
+        CHECK((cs.size() == narrow_cast<std::ptrdiff_t>(cstr.size()) &&
+              cs.data() == cstr.data()));
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        auto get_temp_vector = []() -> std::vector<int> { return {}; };
+        auto use_span = [](span<int> s) { static_cast<void>(s); };
+        use_span(get_temp_vector());
+#endif
+    }
+
+    {
+        auto get_temp_vector = []() -> std::vector<int> { return {}; };
+        auto use_span = [](span<const int> s) { static_cast<void>(s); };
+        use_span(get_temp_vector());
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        auto get_temp_string = []() -> std::string { return {}; };
+        auto use_span = [](span<char> s) { static_cast<void>(s); };
+        use_span(get_temp_string());
+#endif
+    }
+
+    {
+        auto get_temp_string = []() -> std::string { return {}; };
+        auto use_span = [](span<const char> s) { static_cast<void>(s); };
+        use_span(get_temp_string());
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        auto get_temp_vector = []() -> const std::vector<int> { return {}; };
+        auto use_span = [](span<const char> s) { static_cast<void>(s); };
+        use_span(get_temp_vector());
+#endif
+    }
+
+    {
+        auto get_temp_string = []() -> const std::string { return {}; };
+        auto use_span = [](span<const char> s) { static_cast<void>(s); };
+        use_span(get_temp_string());
+    }
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        std::map<int, int> m;
+        span<int> s{m};
+#endif
+    }
+
+    {
+        auto s = make_span(v);
+        CHECK((s.size() == narrow_cast<std::ptrdiff_t>(v.size()) && s.data() == v.data()));
+
+        auto cs = make_span(cv);
+        CHECK((cs.size() == narrow_cast<std::ptrdiff_t>(cv.size()) && cs.data() == cv.data()));
+    }
+}
+
+TEST_CASE("from_convertible_span_constructor")
+{
+    {
+        span<DerivedClass> avd;
+        span<const DerivedClass> avcd = avd;
+        static_cast<void>(avcd);
+    }
+
+    {
+    #ifdef CONFIRM_COMPILATION_ERRORS
+        span<DerivedClass> avd;
+        span<BaseClass> avb = avd;
+        static_cast<void>(avb);
+    #endif
+    }
+
+    #ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        span<int> s;
+        span<unsigned int> s2 = s;
+        static_cast<void>(s2);
+    }
+
+    {
+        span<int> s;
+        span<const unsigned int> s2 = s;
+        static_cast<void>(s2);
+    }
+
+    {
+        span<int> s;
+        span<short> s2 = s;
+        static_cast<void>(s2);
+    }
+    #endif
+}
+
+TEST_CASE("copy_move_and_assignment")
+{
+    span<int> s1;
+    CHECK(s1.empty());
+
+    int arr[] = {3, 4, 5};
+
+    span<const int> s2 = arr;
+    CHECK((s2.size() == 3 && s2.data() == &arr[0]));
+
+    s2 = s1;
+    CHECK(s2.empty());
+
+    auto get_temp_span = [&]() -> span<int> { return {&arr[1], 2}; };
+    auto use_span = [&](span<const int> s) { CHECK((s.size() == 2 && s.data() == &arr[1])); };
+    use_span(get_temp_span());
+
+    s1 = get_temp_span();
+    CHECK((s1.size() == 2 && s1.data() == &arr[1]));
+}
+
+TEST_CASE("first")
+{
+    int arr[5] = {1, 2, 3, 4, 5};
+
+    {
+        span<int, 5> av = arr;
+        CHECK(av.first<2>().size() == 2);
+        CHECK(av.first(2).size() == 2);
+    }
+
+    {
+        span<int, 5> av = arr;
+        CHECK(av.first<0>().size() == 0);
+        CHECK(av.first(0).size() == 0);
+    }
+
+    {
+        span<int, 5> av = arr;
+        CHECK(av.first<5>().size() == 5);
+        CHECK(av.first(5).size() == 5);
+    }
+
+    {
+        span<int, 5> av = arr;
+#ifdef CONFIRM_COMPILATION_ERRORS
+        CHECK(av.first<6>().size() == 6);
+        CHECK(av.first<-1>().size() == -1);
+#endif
+        CHECK_THROWS_AS(av.first(6).size(), fail_fast);
+    }
+
+    {
+        span<int> av;
+        CHECK(av.first<0>().size() == 0);
+        CHECK(av.first(0).size() == 0);
+    }
+}
+
+TEST_CASE("last")
+{
+    int arr[5] = {1, 2, 3, 4, 5};
+
+    {
+        span<int, 5> av = arr;
+        CHECK(av.last<2>().size() == 2);
+        CHECK(av.last(2).size() == 2);
+    }
+
+    {
+        span<int, 5> av = arr;
+        CHECK(av.last<0>().size() == 0);
+        CHECK(av.last(0).size() == 0);
+    }
+
+    {
+        span<int, 5> av = arr;
+        CHECK(av.last<5>().size() == 5);
+        CHECK(av.last(5).size() == 5);
+    }
+
+    {
+        span<int, 5> av = arr;
+#ifdef CONFIRM_COMPILATION_ERRORS
+        CHECK(av.last<6>().size() == 6);
+#endif
+        CHECK_THROWS_AS(av.last(6).size(), fail_fast);
+    }
+
+    {
+        span<int> av;
+        CHECK(av.last<0>().size() == 0);
+        CHECK(av.last(0).size() == 0);
+    }
+}
+
+TEST_CASE("subspan")
+{
+    int arr[5] = {1, 2, 3, 4, 5};
+
+    {
+        span<int, 5> av = arr;
+        CHECK((av.subspan<2, 2>().size() == 2));
+        CHECK(decltype(av.subspan<2, 2>())::extent == 2);
+        CHECK(av.subspan(2, 2).size() == 2);
+        CHECK(av.subspan(2, 3).size() == 3);
+    }
+
+    {
+        span<int, 5> av = arr;
+        CHECK((av.subspan<0, 0>().size() == 0));
+        CHECK(decltype(av.subspan<0,0>())::extent == 0);
+        CHECK(av.subspan(0, 0).size() == 0);
+    }
+
+    {
+        span<int, 5> av = arr;
+        CHECK((av.subspan<0, 5>().size() == 5));
+        CHECK(decltype(av.subspan<0, 5>())::extent == 5);
+        CHECK(av.subspan(0, 5).size() == 5);
+
+        CHECK_THROWS_AS(av.subspan(0, 6).size(), fail_fast);
+        CHECK_THROWS_AS(av.subspan(1, 5).size(), fail_fast);
+    }
+
+    {
+        span<int, 5> av = arr;
+        CHECK((av.subspan<4, 0>().size() == 0));
+        CHECK(decltype(av.subspan<4, 0>())::extent == 0);
+        CHECK(av.subspan(4, 0).size() == 0);
+        CHECK(av.subspan(5, 0).size() == 0);
+        CHECK_THROWS_AS(av.subspan(6, 0).size(), fail_fast);
+    }
+
+    {
+        span<int, 5> av = arr;
+        CHECK((av.subspan<1>().size() == 4));
+        CHECK(decltype(av.subspan<1>())::extent == 4);    
+    }
+
+    {
+        span<int> av;
+        CHECK((av.subspan<0, 0>().size() == 0));
+        CHECK((decltype(av.subspan<0, 0>())::extent == 0));
+        CHECK(av.subspan(0, 0).size() == 0);
+        CHECK_THROWS_AS((av.subspan<1, 0>().size()), fail_fast);
+    }
+
+    {
+        span<int> av;
+        CHECK(av.subspan(0).size() == 0);
+        CHECK_THROWS_AS(av.subspan(1).size(), fail_fast);
+    }
+
+    {
+        span<int> av = arr;
+        CHECK(av.subspan(0).size() == 5);
+        CHECK(av.subspan(1).size() == 4);
+        CHECK(av.subspan(4).size() == 1);
+        CHECK(av.subspan(5).size() == 0);
+        CHECK_THROWS_AS(av.subspan(6).size(), fail_fast);
+        const auto av2 = av.subspan(1);
+        for (int i = 0; i < 4; ++i) CHECK(av2[i] == i + 2);
+    }
+
+    {
+        span<int, 5> av = arr;
+        CHECK(av.subspan(0).size() == 5);
+        CHECK(av.subspan(1).size() == 4);
+        CHECK(av.subspan(4).size() == 1);
+        CHECK(av.subspan(5).size() == 0);
+        CHECK_THROWS_AS(av.subspan(6).size(), fail_fast);
+        const auto av2 = av.subspan(1);
+        for (int i = 0; i < 4; ++i) CHECK(av2[i] == i + 2);
+    }
+}
+
+TEST_CASE("at_call")
+{
+    int arr[4] = {1, 2, 3, 4};
+
+    {
+        span<int> s = arr;
+        CHECK(s.at(0) == 1);
+        CHECK_THROWS_AS(s.at(5), fail_fast);
+    }
+
+    {
+        int arr2d[2] = {1, 6};
+        span<int, 2> s = arr2d;
+        CHECK(s.at(0) == 1);
+        CHECK(s.at(1) == 6);
+        CHECK_THROWS_AS(s.at(2), fail_fast);
+    }
+}
+
+TEST_CASE("operator_function_call")
+{
+    int arr[4] = {1, 2, 3, 4};
+
+    {
+        span<int> s = arr;
+        CHECK(s(0) == 1);
+        CHECK_THROWS_AS(s(5), fail_fast);
+    }
+
+    {
+        int arr2d[2] = {1, 6};
+        span<int, 2> s = arr2d;
+        CHECK(s(0) == 1);
+        CHECK(s(1) == 6);
+        CHECK_THROWS_AS(s(2), fail_fast);
+    }
+}
+
+TEST_CASE("iterator_default_init")
+{
+    span<int>::iterator it1;
+    span<int>::iterator it2;
+    CHECK(it1 == it2);
+}
+
+TEST_CASE("const_iterator_default_init")
+{
+    span<int>::const_iterator it1;
+    span<int>::const_iterator it2;
+    CHECK(it1 == it2);
+}
+
+TEST_CASE("iterator_conversions")
+{
+    span<int>::iterator badIt;
+    span<int>::const_iterator badConstIt;
+    CHECK(badIt == badConstIt);
+
+    int a[] = {1, 2, 3, 4};
+    span<int> s = a;
+
+    auto it = s.begin();
+    auto cit = s.cbegin();
+
+    CHECK(it == cit);
+    CHECK(cit == it);
+
+    span<int>::const_iterator cit2 = it;
+    CHECK(cit2 == cit);
+
+    span<int>::const_iterator cit3 = it + 4;
+    CHECK(cit3 == s.cend());
+}
+
+TEST_CASE("iterator_comparisons")
+{
+    int a[] = {1, 2, 3, 4};
+    {
+        span<int> s = a;
+        span<int>::iterator it = s.begin();
+        auto it2 = it + 1;
+        span<int>::const_iterator cit = s.cbegin();
+
+        CHECK(it == cit);
+        CHECK(cit == it);
+        CHECK(it == it);
+        CHECK(cit == cit);
+        CHECK(cit == s.begin());
+        CHECK(s.begin() == cit);
+        CHECK(s.cbegin() == cit);
+        CHECK(it == s.begin());
+        CHECK(s.begin() == it);
+
+        CHECK(it != it2);
+        CHECK(it2 != it);
+        CHECK(it != s.end());
+        CHECK(it2 != s.end());
+        CHECK(s.end() != it);
+        CHECK(it2 != cit);
+        CHECK(cit != it2);
+
+        CHECK(it < it2);
+        CHECK(it <= it2);
+        CHECK(it2 <= s.end());
+        CHECK(it < s.end());
+        CHECK(it <= cit);
+        CHECK(cit <= it);
+        CHECK(cit < it2);
+        CHECK(cit <= it2);
+        CHECK(cit < s.end());
+        CHECK(cit <= s.end());
+
+        CHECK(it2 > it);
+        CHECK(it2 >= it);
+        CHECK(s.end() > it2);
+        CHECK(s.end() >= it2);
+        CHECK(it2 > cit);
+        CHECK(it2 >= cit);
+    }
+}
+
+TEST_CASE("begin_end")
+{
+    {
+        int a[] = {1, 2, 3, 4};
+        span<int> s = a;
+
+        span<int>::iterator it = s.begin();
+        span<int>::iterator it2 = std::begin(s);
+        CHECK(it == it2);
+
+        it = s.end();
+        it2 = std::end(s);
+        CHECK(it == it2);
+    }
+
+    {
+        int a[] = {1, 2, 3, 4};
+        span<int> s = a;
+
+        auto it = s.begin();
+        auto first = it;
+        CHECK(it == first);
+        CHECK(*it == 1);
+
+        auto beyond = s.end();
+        CHECK(it != beyond);
+        CHECK_THROWS_AS(*beyond, fail_fast);
+
+        CHECK(beyond - first == 4);
+        CHECK(first - first == 0);
+        CHECK(beyond - beyond == 0);
+
+        ++it;
+        CHECK(it - first == 1);
+        CHECK(*it == 2);
+        *it = 22;
+        CHECK(*it == 22);
+        CHECK(beyond - it == 3);
+
+        it = first;
+        CHECK(it == first);
+        while (it != s.end()) {
+            *it = 5;
+            ++it;
+        }
+
+        CHECK(it == beyond);
+        CHECK(it - beyond == 0);
+
+        for (const auto& n : s) {
+            CHECK(n == 5);
+        }
+    }
+}
+
+TEST_CASE("cbegin_cend")
+{
+    {
+        int a[] = {1, 2, 3, 4};
+        span<int> s = a;
+
+        span<int>::const_iterator cit = s.cbegin();
+        span<int>::const_iterator cit2 = std::cbegin(s);
+        CHECK(cit == cit2);
+
+        cit = s.cend();
+        cit2 = std::cend(s);
+        CHECK(cit == cit2);
+    }
+
+    {
+        int a[] = {1, 2, 3, 4};
+        span<int> s = a;
+
+        auto it = s.cbegin();
+        auto first = it;
+        CHECK(it == first);
+        CHECK(*it == 1);
+
+        auto beyond = s.cend();
+        CHECK(it != beyond);
+        CHECK_THROWS_AS(*beyond, fail_fast);
+
+        CHECK(beyond - first == 4);
+        CHECK(first - first == 0);
+        CHECK(beyond - beyond == 0);
+
+        ++it;
+        CHECK(it - first == 1);
+        CHECK(*it == 2);
+        CHECK(beyond - it == 3);
+
+        int last = 0;
+        it = first;
+        CHECK(it == first);
+        while (it != s.cend()) {
+            CHECK(*it == last + 1);
+
+            last = *it;
+            ++it;
+        }
+
+        CHECK(it == beyond);
+        CHECK(it - beyond == 0);
+    }
+}
+
+TEST_CASE("rbegin_rend")
+{
+    {
+        int a[] = {1, 2, 3, 4};
+        span<int> s = a;
+
+        auto it = s.rbegin();
+        auto first = it;
+        CHECK(it == first);
+        CHECK(*it == 4);
+
+        auto beyond = s.rend();
+        CHECK(it != beyond);
+        CHECK_THROWS_AS(*beyond, fail_fast);
+
+        CHECK(beyond - first == 4);
+        CHECK(first - first == 0);
+        CHECK(beyond - beyond == 0);
+
+        ++it;
+        CHECK(it - first == 1);
+        CHECK(*it == 3);
+        *it = 22;
+        CHECK(*it == 22);
+        CHECK(beyond - it == 3);
+
+        it = first;
+        CHECK(it == first);
+        while (it != s.rend()) {
+            *it = 5;
+            ++it;
+        }
+
+        CHECK(it == beyond);
+        CHECK(it - beyond == 0);
+
+        for (const auto& n : s) {
+            CHECK(n == 5);
+        }
+    }
+}
+
+TEST_CASE("crbegin_crend")
+{
+    {
+        int a[] = {1, 2, 3, 4};
+        span<int> s = a;
+
+        auto it = s.crbegin();
+        auto first = it;
+        CHECK(it == first);
+        CHECK(*it == 4);
+
+        auto beyond = s.crend();
+        CHECK(it != beyond);
+        CHECK_THROWS_AS(*beyond, fail_fast);
+
+        CHECK(beyond - first == 4);
+        CHECK(first - first == 0);
+        CHECK(beyond - beyond == 0);
+
+        ++it;
+        CHECK(it - first == 1);
+        CHECK(*it == 3);
+        CHECK(beyond - it == 3);
+
+        it = first;
+        CHECK(it == first);
+        int last = 5;
+        while (it != s.crend()) {
+            CHECK(*it == last - 1);
+            last = *it;
+
+            ++it;
+        }
+
+        CHECK(it == beyond);
+        CHECK(it - beyond == 0);
+    }
+}
+
+TEST_CASE("comparison_operators")
+{
+    {
+        span<int> s1;
+        span<int> s2;
+        CHECK(s1 == s2);
+        CHECK(!(s1 != s2));
+        CHECK(!(s1 < s2));
+        CHECK(s1 <= s2);
+        CHECK(!(s1 > s2));
+        CHECK(s1 >= s2);
+        CHECK(s2 == s1);
+        CHECK(!(s2 != s1));
+        CHECK(!(s2 < s1));
+        CHECK(s2 <= s1);
+        CHECK(!(s2 > s1));
+        CHECK(s2 >= s1);
+    }
+
+    {
+        int arr[] = {2, 1};
+        span<int> s1 = arr;
+        span<int> s2 = arr;
+
+        CHECK(s1 == s2);
+        CHECK(!(s1 != s2));
+        CHECK(!(s1 < s2));
+        CHECK(s1 <= s2);
+        CHECK(!(s1 > s2));
+        CHECK(s1 >= s2);
+        CHECK(s2 == s1);
+        CHECK(!(s2 != s1));
+        CHECK(!(s2 < s1));
+        CHECK(s2 <= s1);
+        CHECK(!(s2 > s1));
+        CHECK(s2 >= s1);
+    }
+
+    {
+        int arr[] = {2, 1}; // bigger
+
+        span<int> s1;
+        span<int> s2 = arr;
+
+        CHECK(s1 != s2);
+        CHECK(s2 != s1);
+        CHECK(!(s1 == s2));
+        CHECK(!(s2 == s1));
+        CHECK(s1 < s2);
+        CHECK(!(s2 < s1));
+        CHECK(s1 <= s2);
+        CHECK(!(s2 <= s1));
+        CHECK(s2 > s1);
+        CHECK(!(s1 > s2));
+        CHECK(s2 >= s1);
+        CHECK(!(s1 >= s2));
+    }
+
+    {
+        int arr1[] = {1, 2};
+        int arr2[] = {1, 2};
+        span<int> s1 = arr1;
+        span<int> s2 = arr2;
+
+        CHECK(s1 == s2);
+        CHECK(!(s1 != s2));
+        CHECK(!(s1 < s2));
+        CHECK(s1 <= s2);
+        CHECK(!(s1 > s2));
+        CHECK(s1 >= s2);
+        CHECK(s2 == s1);
+        CHECK(!(s2 != s1));
+        CHECK(!(s2 < s1));
+        CHECK(s2 <= s1);
+        CHECK(!(s2 > s1));
+        CHECK(s2 >= s1);
+    }
+
+    {
+        int arr[] = {1, 2, 3};
+
+        span<int> s1 = {&arr[0], 2}; // shorter
+        span<int> s2 = arr;          // longer
+
+        CHECK(s1 != s2);
+        CHECK(s2 != s1);
+        CHECK(!(s1 == s2));
+        CHECK(!(s2 == s1));
+        CHECK(s1 < s2);
+        CHECK(!(s2 < s1));
+        CHECK(s1 <= s2);
+        CHECK(!(s2 <= s1));
+        CHECK(s2 > s1);
+        CHECK(!(s1 > s2));
+        CHECK(s2 >= s1);
+        CHECK(!(s1 >= s2));
+    }
+
+    {
+        int arr1[] = {1, 2}; // smaller
+        int arr2[] = {2, 1}; // bigger
+
+        span<int> s1 = arr1;
+        span<int> s2 = arr2;
+
+        CHECK(s1 != s2);
+        CHECK(s2 != s1);
+        CHECK(!(s1 == s2));
+        CHECK(!(s2 == s1));
+        CHECK(s1 < s2);
+        CHECK(!(s2 < s1));
+        CHECK(s1 <= s2);
+        CHECK(!(s2 <= s1));
+        CHECK(s2 > s1);
+        CHECK(!(s1 > s2));
+        CHECK(s2 >= s1);
+        CHECK(!(s1 >= s2));
+    }
+}
+
+TEST_CASE("as_bytes")
+{
+    int a[] = {1, 2, 3, 4};
+
+    {
+        const span<const int> s = a;
+        CHECK(s.size() == 4);
+        const span<const byte> bs = as_bytes(s);
+        CHECK(static_cast<const void*>(bs.data()) == static_cast<const void*>(s.data()));
+        CHECK(bs.size() == s.size_bytes());
+    }
+
+    {
+        span<int> s;
+        const auto bs = as_bytes(s);
+        CHECK(bs.size() == s.size());
+        CHECK(bs.size() == 0);
+        CHECK(bs.size_bytes() == 0);
+        CHECK(static_cast<const void*>(bs.data()) == static_cast<const void*>(s.data()));
+        CHECK(bs.data() == nullptr);
+    }
+
+    {
+        span<int> s = a;
+        const auto bs = as_bytes(s);
+        CHECK(static_cast<const void*>(bs.data()) == static_cast<const void*>(s.data()));
+        CHECK(bs.size() == s.size_bytes());
+    }
+}
+
+TEST_CASE("as_writeable_bytes")
+{
+    int a[] = {1, 2, 3, 4};
+
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        // you should not be able to get writeable bytes for const objects
+        span<const int> s = a;
+        CHECK(s.size() == 4);
+        span<const byte> bs = as_writeable_bytes(s);
+        CHECK(static_cast<void*>(bs.data()) == static_cast<void*>(s.data()));
+        CHECK(bs.size() == s.size_bytes());
+#endif
+    }
+
+    {
+        span<int> s;
+        const auto bs = as_writeable_bytes(s);
+        CHECK(bs.size() == s.size());
+        CHECK(bs.size() == 0);
+        CHECK(bs.size_bytes() == 0);
+        CHECK(static_cast<void*>(bs.data()) == static_cast<void*>(s.data()));
+        CHECK(bs.data() == nullptr);
+    }
+
+    {
+        span<int> s = a;
+        const auto bs = as_writeable_bytes(s);
+        CHECK(static_cast<void*>(bs.data()) == static_cast<void*>(s.data()));
+        CHECK(bs.size() == s.size_bytes());
+    }
+}
+
+TEST_CASE("fixed_size_conversions")
+{
+    int arr[] = {1, 2, 3, 4};
+
+    // converting to an span from an equal size array is ok
+    span<int, 4> s4 = arr;
+    CHECK(s4.size() == 4);
+
+    // converting to dynamic_range is always ok
+    {
+        span<int> s = s4;
+        CHECK(s.size() == s4.size());
+        static_cast<void>(s);
+    }
+
+// initialization or assignment to static span that REDUCES size is NOT ok
+#ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        span<int, 2> s = arr;
+    }
+    {
+        span<int, 2> s2 = s4;
+        static_cast<void>(s2);
+    }
+#endif
+
+    // even when done dynamically
+    {
+        span<int> s = arr;
+        auto f = [&]() {
+            span<int, 2> s2 = s;
+            static_cast<void>(s2);
+        };
+        CHECK_THROWS_AS(f(), fail_fast);
+    }
+
+    // but doing so explicitly is ok
+
+    // you can convert statically
+    {
+        const span<int, 2> s2 = {arr, 2};
+        static_cast<void>(s2);
+    }
+    {
+        const span<int, 1> s1 = s4.first<1>();
+        static_cast<void>(s1);
+    }
+
+    // ...or dynamically
+    {
+        // NB: implicit conversion to span<int,1> from span<int>
+        span<int, 1> s1 = s4.first(1);
+        static_cast<void>(s1);
+    }
+
+    // initialization or assignment to static span that requires size INCREASE is not ok.
+    int arr2[2] = {1, 2};
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        span<int, 4> s3 = arr2;
+    }
+    {
+        span<int, 2> s2 = arr2;
+        span<int, 4> s4a = s2;
+    }
+#endif
+    {
+        auto f = [&]() {
+            span<int, 4> _s4 = {arr2, 2};
+            static_cast<void>(_s4);
+        };
+        CHECK_THROWS_AS(f(), fail_fast);
+    }
+
+    // this should fail - we are trying to assign a small dynamic span to a fixed_size larger one
+    span<int> av = arr2;
+    auto f = [&]() {
+        span<int, 4> _s4 = av;
+        static_cast<void>(_s4);
+    };
+    CHECK_THROWS_AS(f(), fail_fast);
+}
+
+TEST_CASE("interop_with_std_regex")
+{
+    char lat[] = {'1', '2', '3', '4', '5', '6', 'E', 'F', 'G'};
+    span<char> s = lat;
+    const auto f_it = s.begin() + 7;
+
+    std::match_results<span<char>::iterator> match;
+
+    std::regex_match(s.begin(), s.end(), match, std::regex(".*"));
+    CHECK(match.ready());
+    CHECK(!match.empty());
+    CHECK(match[0].matched);
+    CHECK(match[0].first == s.begin());
+    CHECK(match[0].second == s.end());
+
+    std::regex_search(s.begin(), s.end(), match, std::regex("F"));
+    CHECK(match.ready());
+    CHECK(!match.empty());
+    CHECK(match[0].matched);
+    CHECK(match[0].first == f_it);
+    CHECK(match[0].second == (f_it + 1));
+}
+
+TEST_CASE("interop_with_gsl_at")
+{
+    int arr[5] = {1, 2, 3, 4, 5};
+    span<int> s{arr};
+    CHECK((at(s, 0) == 1 && at(s, 1) == 2));
+}
+
+TEST_CASE("default_constructible")
+{
+    CHECK((std::is_default_constructible<span<int>>::value));
+    CHECK((std::is_default_constructible<span<int, 0>>::value));
+    CHECK((!std::is_default_constructible<span<int, 42>>::value));
+}
diff --git a/tests/strided_span_tests.cpp b/tests/strided_span_tests.cpp
new file mode 100644
index 0000000..8719336
--- /dev/null
+++ b/tests/strided_span_tests.cpp
@@ -0,0 +1,757 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <catch/catch.hpp> // for AssertionHandler, StringRef, CHECK, CHECK...
+
+#include <gsl/gsl_byte>   // for byte
+#include <gsl/gsl_util>   // for narrow_cast
+#include <gsl/multi_span> // for strided_span, index, multi_span, strided_...
+
+#include <iostream>    // for size_t
+#include <iterator>    // for begin, end
+#include <numeric>     // for iota
+#include <type_traits> // for integral_constant<>::value, is_convertible
+#include <vector>      // for vector
+
+namespace gsl {
+struct fail_fast;
+}  // namespace gsl
+
+using namespace std;
+using namespace gsl;
+
+namespace
+{
+struct BaseClass
+{
+};
+struct DerivedClass : BaseClass
+{
+};
+}
+
+TEST_CASE("span_section_test")
+{
+    int a[30][4][5];
+
+    const auto av = as_multi_span(a);
+    const auto sub = av.section({15, 0, 0}, gsl::multi_span_index<3>{2, 2, 2});
+    const auto subsub = sub.section({1, 0, 0}, gsl::multi_span_index<3>{1, 1, 1});
+    (void) subsub;
+}
+
+TEST_CASE("span_section")
+{
+    std::vector<int> data(5 * 10);
+    std::iota(begin(data), end(data), 0);
+    const multi_span<int, 5, 10> av = as_multi_span(multi_span<int>{data}, dim<5>(), dim<10>());
+
+    const strided_span<int, 2> av_section_1 = av.section({1, 2}, {3, 4});
+    CHECK((av_section_1[{0, 0}] == 12));
+    CHECK((av_section_1[{0, 1}] == 13));
+    CHECK((av_section_1[{1, 0}] == 22));
+    CHECK((av_section_1[{2, 3}] == 35));
+
+    const strided_span<int, 2> av_section_2 = av_section_1.section({1, 2}, {2, 2});
+    CHECK((av_section_2[{0, 0}] == 24));
+    CHECK((av_section_2[{0, 1}] == 25));
+    CHECK((av_section_2[{1, 0}] == 34));
+}
+
+TEST_CASE("strided_span_constructors")
+{
+    // Check stride constructor
+    {
+        int arr[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
+        const int carr[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
+
+        strided_span<int, 1> sav1{arr, {{9}, {1}}}; // T -> T
+        CHECK(sav1.bounds().index_bounds() == multi_span_index<1>{9});
+        CHECK(sav1.bounds().stride() == 1);
+        CHECK((sav1[0] == 1 && sav1[8] == 9));
+
+        strided_span<const int, 1> sav2{carr, {{4}, {2}}}; // const T -> const T
+        CHECK(sav2.bounds().index_bounds() == multi_span_index<1>{4});
+        CHECK(sav2.bounds().strides() == multi_span_index<1>{2});
+        CHECK((sav2[0] == 1 && sav2[3] == 7));
+
+        strided_span<int, 2> sav3{arr, {{2, 2}, {6, 2}}}; // T -> const T
+        CHECK((sav3.bounds().index_bounds() == multi_span_index<2>{2, 2}));
+        CHECK((sav3.bounds().strides() == multi_span_index<2>{6, 2}));
+        CHECK((sav3[{0, 0}] == 1 && sav3[{0, 1}] == 3 && sav3[{1, 0}] == 7));
+    }
+
+    // Check multi_span constructor
+    {
+        int arr[] = {1, 2};
+
+        // From non-cv-qualified source
+        {
+            const multi_span<int> src = arr;
+
+            strided_span<int, 1> sav{src, {2, 1}};
+            CHECK(sav.bounds().index_bounds() == multi_span_index<1>{2});
+            CHECK(sav.bounds().strides() == multi_span_index<1>{1});
+            CHECK(sav[1] == 2);
+
+#if _MSC_VER > 1800
+            // strided_span<const int, 1> sav_c{ {src}, {2, 1} };
+            strided_span<const int, 1> sav_c{multi_span<const int>{src},
+                                             strided_bounds<1>{2, 1}};
+#else
+            strided_span<const int, 1> sav_c{multi_span<const int>{src},
+                                             strided_bounds<1>{2, 1}};
+#endif
+            CHECK(sav_c.bounds().index_bounds() == multi_span_index<1>{2});
+            CHECK(sav_c.bounds().strides() == multi_span_index<1>{1});
+            CHECK(sav_c[1] == 2);
+
+#if _MSC_VER > 1800
+            strided_span<volatile int, 1> sav_v{src, {2, 1}};
+#else
+            strided_span<volatile int, 1> sav_v{multi_span<volatile int>{src},
+                                                strided_bounds<1>{2, 1}};
+#endif
+            CHECK(sav_v.bounds().index_bounds() == multi_span_index<1>{2});
+            CHECK(sav_v.bounds().strides() == multi_span_index<1>{1});
+            CHECK(sav_v[1] == 2);
+
+#if _MSC_VER > 1800
+            strided_span<const volatile int, 1> sav_cv{src, {2, 1}};
+#else
+            strided_span<const volatile int, 1> sav_cv{multi_span<const volatile int>{src},
+                                                       strided_bounds<1>{2, 1}};
+#endif
+            CHECK(sav_cv.bounds().index_bounds() == multi_span_index<1>{2});
+            CHECK(sav_cv.bounds().strides() == multi_span_index<1>{1});
+            CHECK(sav_cv[1] == 2);
+        }
+
+        // From const-qualified source
+        {
+            const multi_span<const int> src{arr};
+
+            strided_span<const int, 1> sav_c{src, {2, 1}};
+            CHECK(sav_c.bounds().index_bounds() == multi_span_index<1>{2});
+            CHECK(sav_c.bounds().strides() == multi_span_index<1>{1});
+            CHECK(sav_c[1] == 2);
+
+#if _MSC_VER > 1800
+            strided_span<const volatile int, 1> sav_cv{src, {2, 1}};
+#else
+            strided_span<const volatile int, 1> sav_cv{multi_span<const volatile int>{src},
+                                                       strided_bounds<1>{2, 1}};
+#endif
+
+            CHECK(sav_cv.bounds().index_bounds() == multi_span_index<1>{2});
+            CHECK(sav_cv.bounds().strides() == multi_span_index<1>{1});
+            CHECK(sav_cv[1] == 2);
+        }
+
+        // From volatile-qualified source
+        {
+            const multi_span<volatile int> src{arr};
+
+            strided_span<volatile int, 1> sav_v{src, {2, 1}};
+            CHECK(sav_v.bounds().index_bounds() == multi_span_index<1>{2});
+            CHECK(sav_v.bounds().strides() == multi_span_index<1>{1});
+            CHECK(sav_v[1] == 2);
+
+#if _MSC_VER > 1800
+            strided_span<const volatile int, 1> sav_cv{src, {2, 1}};
+#else
+            strided_span<const volatile int, 1> sav_cv{multi_span<const volatile int>{src},
+                                                       strided_bounds<1>{2, 1}};
+#endif
+            CHECK(sav_cv.bounds().index_bounds() == multi_span_index<1>{2});
+            CHECK(sav_cv.bounds().strides() == multi_span_index<1>{1});
+            CHECK(sav_cv[1] == 2);
+        }
+
+        // From cv-qualified source
+        {
+            const multi_span<const volatile int> src{arr};
+
+            strided_span<const volatile int, 1> sav_cv{src, {2, 1}};
+            CHECK(sav_cv.bounds().index_bounds() == multi_span_index<1>{2});
+            CHECK(sav_cv.bounds().strides() == multi_span_index<1>{1});
+            CHECK(sav_cv[1] == 2);
+        }
+    }
+
+    // Check const-casting constructor
+    {
+        int arr[2] = {4, 5};
+
+        const multi_span<int, 2> av(arr, 2);
+        multi_span<const int, 2> av2{av};
+        CHECK(av2[1] == 5);
+
+        static_assert(
+            std::is_convertible<const multi_span<int, 2>, multi_span<const int, 2>>::value,
+            "ctor is not implicit!");
+
+        const strided_span<int, 1> src{arr, {2, 1}};
+        strided_span<const int, 1> sav{src};
+        CHECK(sav.bounds().index_bounds() == multi_span_index<1>{2});
+        CHECK(sav.bounds().stride() == 1);
+        CHECK(sav[1] == 5);
+
+        static_assert(
+            std::is_convertible<const strided_span<int, 1>, strided_span<const int, 1>>::value,
+            "ctor is not implicit!");
+    }
+
+    // Check copy constructor
+    {
+        int arr1[2] = {3, 4};
+        const strided_span<int, 1> src1{arr1, {2, 1}};
+        strided_span<int, 1> sav1{src1};
+
+        CHECK(sav1.bounds().index_bounds() == multi_span_index<1>{2});
+        CHECK(sav1.bounds().stride() == 1);
+        CHECK(sav1[0] == 3);
+
+        int arr2[6] = {1, 2, 3, 4, 5, 6};
+        const strided_span<const int, 2> src2{arr2, {{3, 2}, {2, 1}}};
+        strided_span<const int, 2> sav2{src2};
+        CHECK((sav2.bounds().index_bounds() == multi_span_index<2>{3, 2}));
+        CHECK((sav2.bounds().strides() == multi_span_index<2>{2, 1}));
+        CHECK((sav2[{0, 0}] == 1 && sav2[{2, 0}] == 5));
+    }
+
+    // Check const-casting assignment operator
+    {
+        int arr1[2] = {1, 2};
+        int arr2[6] = {3, 4, 5, 6, 7, 8};
+
+        const strided_span<int, 1> src{arr1, {{2}, {1}}};
+        strided_span<const int, 1> sav{arr2, {{3}, {2}}};
+        strided_span<const int, 1>& sav_ref = (sav = src);
+        CHECK(sav.bounds().index_bounds() == multi_span_index<1>{2});
+        CHECK(sav.bounds().strides() == multi_span_index<1>{1});
+        CHECK(sav[0] == 1);
+        CHECK(&sav_ref == &sav);
+    }
+
+    // Check copy assignment operator
+    {
+        int arr1[2] = {3, 4};
+        int arr1b[1] = {0};
+        const strided_span<int, 1> src1{arr1, {2, 1}};
+        strided_span<int, 1> sav1{arr1b, {1, 1}};
+        strided_span<int, 1>& sav1_ref = (sav1 = src1);
+        CHECK(sav1.bounds().index_bounds() == multi_span_index<1>{2});
+        CHECK(sav1.bounds().strides() == multi_span_index<1>{1});
+        CHECK(sav1[0] == 3);
+        CHECK(&sav1_ref == &sav1);
+
+        const int arr2[6] = {1, 2, 3, 4, 5, 6};
+        const int arr2b[1] = {0};
+        const strided_span<const int, 2> src2{arr2, {{3, 2}, {2, 1}}};
+        strided_span<const int, 2> sav2{arr2b, {{1, 1}, {1, 1}}};
+        strided_span<const int, 2>& sav2_ref = (sav2 = src2);
+        CHECK((sav2.bounds().index_bounds() == multi_span_index<2>{3, 2}));
+        CHECK((sav2.bounds().strides() == multi_span_index<2>{2, 1}));
+        CHECK((sav2[{0, 0}] == 1 && sav2[{2, 0}] == 5));
+        CHECK(&sav2_ref == &sav2);
+    }
+}
+
+TEST_CASE("strided_span_slice")
+{
+    std::vector<int> data(5 * 10);
+    std::iota(begin(data), end(data), 0);
+    const multi_span<int, 5, 10> src =
+        as_multi_span(multi_span<int>{data}, dim<5>(), dim<10>());
+
+    const strided_span<int, 2> sav{src, {{5, 10}, {10, 1}}};
+#ifdef CONFIRM_COMPILATION_ERRORS
+    const strided_span<const int, 2> csav{{src}, {{5, 10}, {10, 1}}};
+#endif
+    const strided_span<const int, 2> csav{multi_span<const int, 5, 10>{src},
+                                          {{5, 10}, {10, 1}}};
+
+    strided_span<int, 1> sav_sl = sav[2];
+    CHECK(sav_sl[0] == 20);
+    CHECK(sav_sl[9] == 29);
+
+    strided_span<const int, 1> csav_sl = sav[3];
+    CHECK(csav_sl[0] == 30);
+    CHECK(csav_sl[9] == 39);
+
+    CHECK(sav[4][0] == 40);
+    CHECK(sav[4][9] == 49);
+}
+
+TEST_CASE("strided_span_column_major")
+{
+    // strided_span may be used to accommodate more peculiar
+    // use cases, such as column-major multidimensional array
+    // (aka. "FORTRAN" layout).
+
+    int cm_array[3 * 5] = {1, 4, 7, 10, 13, 2, 5, 8, 11, 14, 3, 6, 9, 12, 15};
+    strided_span<int, 2> cm_sav{cm_array, {{5, 3}, {1, 5}}};
+
+    // Accessing elements
+    CHECK((cm_sav[{0, 0}] == 1));
+    CHECK((cm_sav[{0, 1}] == 2));
+    CHECK((cm_sav[{1, 0}] == 4));
+    CHECK((cm_sav[{4, 2}] == 15));
+
+    // Slice
+    strided_span<int, 1> cm_sl = cm_sav[3];
+
+    CHECK(cm_sl[0] == 10);
+    CHECK(cm_sl[1] == 11);
+    CHECK(cm_sl[2] == 12);
+
+    // Section
+    strided_span<int, 2> cm_sec = cm_sav.section({2, 1}, {3, 2});
+
+    CHECK((cm_sec.bounds().index_bounds() == multi_span_index<2>{3, 2}));
+    CHECK((cm_sec[{0, 0}] == 8));
+    CHECK((cm_sec[{0, 1}] == 9));
+    CHECK((cm_sec[{1, 0}] == 11));
+    CHECK((cm_sec[{2, 1}] == 15));
+}
+
+TEST_CASE("strided_span_bounds")
+{
+    int arr[] = {0, 1, 2, 3};
+    multi_span<int> av(arr);
+
+    {
+        // incorrect sections
+
+        CHECK_THROWS_AS(av.section(0, 0)[0], fail_fast);
+        CHECK_THROWS_AS(av.section(1, 0)[0], fail_fast);
+        CHECK_THROWS_AS(av.section(1, 1)[1], fail_fast);
+
+        CHECK_THROWS_AS(av.section(2, 5), fail_fast);
+        CHECK_THROWS_AS(av.section(5, 2), fail_fast);
+        CHECK_THROWS_AS(av.section(5, 0), fail_fast);
+        CHECK_THROWS_AS(av.section(0, 5), fail_fast);
+        CHECK_THROWS_AS(av.section(5, 5), fail_fast);
+    }
+
+    {
+        // zero stride
+        strided_span<int, 1> sav{av, {{4}, {}}};
+        CHECK(sav[0] == 0);
+        CHECK(sav[3] == 0);
+        CHECK_THROWS_AS(sav[4], fail_fast);
+    }
+
+    {
+        // zero extent
+        strided_span<int, 1> sav{av, {{}, {1}}};
+        CHECK_THROWS_AS(sav[0], fail_fast);
+    }
+
+    {
+        // zero extent and stride
+        strided_span<int, 1> sav{av, {{}, {}}};
+        CHECK_THROWS_AS(sav[0], fail_fast);
+    }
+
+    {
+        // strided array ctor with matching strided bounds
+        strided_span<int, 1> sav{arr, {4, 1}};
+        CHECK(sav.bounds().index_bounds() == multi_span_index<1>{4});
+        CHECK(sav[3] == 3);
+        CHECK_THROWS_AS(sav[4], fail_fast);
+    }
+
+    {
+        // strided array ctor with smaller strided bounds
+        strided_span<int, 1> sav{arr, {2, 1}};
+        CHECK(sav.bounds().index_bounds() == multi_span_index<1>{2});
+        CHECK(sav[1] == 1);
+        CHECK_THROWS_AS(sav[2], fail_fast);
+    }
+
+    {
+        // strided array ctor with fitting irregular bounds
+        strided_span<int, 1> sav{arr, {2, 3}};
+        CHECK(sav.bounds().index_bounds() == multi_span_index<1>{2});
+        CHECK(sav[0] == 0);
+        CHECK(sav[1] == 3);
+        CHECK_THROWS_AS(sav[2], fail_fast);
+    }
+
+    {
+        // bounds cross data boundaries - from static arrays
+        CHECK_THROWS_AS((strided_span<int, 1>{arr, {3, 2}}), fail_fast);
+        CHECK_THROWS_AS((strided_span<int, 1>{arr, {3, 3}}), fail_fast);
+        CHECK_THROWS_AS((strided_span<int, 1>{arr, {4, 5}}), fail_fast);
+        CHECK_THROWS_AS((strided_span<int, 1>{arr, {5, 1}}), fail_fast);
+        CHECK_THROWS_AS((strided_span<int, 1>{arr, {5, 5}}), fail_fast);
+    }
+
+    {
+        // bounds cross data boundaries - from array view
+        CHECK_THROWS_AS((strided_span<int, 1>{av, {3, 2}}), fail_fast);
+        CHECK_THROWS_AS((strided_span<int, 1>{av, {3, 3}}), fail_fast);
+        CHECK_THROWS_AS((strided_span<int, 1>{av, {4, 5}}), fail_fast);
+        CHECK_THROWS_AS((strided_span<int, 1>{av, {5, 1}}), fail_fast);
+        CHECK_THROWS_AS((strided_span<int, 1>{av, {5, 5}}), fail_fast);
+    }
+
+    {
+        // bounds cross data boundaries - from dynamic arrays
+        CHECK_THROWS_AS((strided_span<int, 1>{av.data(), 4, {3, 2}}), fail_fast);
+        CHECK_THROWS_AS((strided_span<int, 1>{av.data(), 4, {3, 3}}), fail_fast);
+        CHECK_THROWS_AS((strided_span<int, 1>{av.data(), 4, {4, 5}}), fail_fast);
+        CHECK_THROWS_AS((strided_span<int, 1>{av.data(), 4, {5, 1}}), fail_fast);
+        CHECK_THROWS_AS((strided_span<int, 1>{av.data(), 4, {5, 5}}), fail_fast);
+        CHECK_THROWS_AS((strided_span<int, 1>{av.data(), 2, {2, 2}}), fail_fast);
+    }
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        strided_span<int, 1> sav0{av.data(), {3, 2}};
+        strided_span<int, 1> sav1{arr, {1}};
+        strided_span<int, 1> sav2{arr, {1, 1, 1}};
+        strided_span<int, 1> sav3{av, {1}};
+        strided_span<int, 1> sav4{av, {1, 1, 1}};
+        strided_span<int, 2> sav5{av.as_multi_span(dim<2>(), dim<2>()), {1}};
+        strided_span<int, 2> sav6{av.as_multi_span(dim<2>(), dim<2>()), {1, 1, 1}};
+        strided_span<int, 2> sav7{av.as_multi_span(dim<2>(), dim<2>()),
+                                  {{1, 1}, {1, 1}, {1, 1}}};
+
+        multi_span_index<1> index{0, 1};
+        strided_span<int, 1> sav8{arr, {1, {1, 1}}};
+        strided_span<int, 1> sav9{arr, {{1, 1}, {1, 1}}};
+        strided_span<int, 1> sav10{av, {1, {1, 1}}};
+        strided_span<int, 1> sav11{av, {{1, 1}, {1, 1}}};
+        strided_span<int, 2> sav12{av.as_multi_span(dim<2>(), dim<2>()), {{1}, {1}}};
+        strided_span<int, 2> sav13{av.as_multi_span(dim<2>(), dim<2>()), {{1}, {1, 1, 1}}};
+        strided_span<int, 2> sav14{av.as_multi_span(dim<2>(), dim<2>()), {{1, 1, 1}, {1}}};
+    }
+#endif
+}
+
+TEST_CASE("strided_span_type_conversion")
+{
+    int arr[] = {0, 1, 2, 3};
+    multi_span<int> av(arr);
+
+    {
+        strided_span<int, 1> sav{av.data(), av.size(), {av.size() / 2, 2}};
+#ifdef CONFIRM_COMPILATION_ERRORS
+        strided_span<long, 1> lsav1 = sav.as_strided_span<long, 1>();
+#endif
+    }
+    {
+        strided_span<int, 1> sav{av, {av.size() / 2, 2}};
+#ifdef CONFIRM_COMPILATION_ERRORS
+        strided_span<long, 1> lsav1 = sav.as_strided_span<long, 1>();
+#endif
+    }
+
+    multi_span<const byte, dynamic_range> bytes = as_bytes(av);
+
+    // retype strided array with regular strides - from raw data
+    {
+        strided_bounds<2> bounds{{2, bytes.size() / 4}, {bytes.size() / 2, 1}};
+        strided_span<const byte, 2> sav2{bytes.data(), bytes.size(), bounds};
+        strided_span<const int, 2> sav3 = sav2.as_strided_span<const int>();
+        CHECK(sav3[0][0] == 0);
+        CHECK(sav3[1][0] == 2);
+        CHECK_THROWS_AS(sav3[1][1], fail_fast);
+        CHECK_THROWS_AS(sav3[0][1], fail_fast);
+    }
+
+    // retype strided array with regular strides - from multi_span
+    {
+        strided_bounds<2> bounds{{2, bytes.size() / 4}, {bytes.size() / 2, 1}};
+        multi_span<const byte, 2, dynamic_range> bytes2 =
+            as_multi_span(bytes, dim<2>(), dim(bytes.size() / 2));
+        strided_span<const byte, 2> sav2{bytes2, bounds};
+        strided_span<int, 2> sav3 = sav2.as_strided_span<int>();
+        CHECK(sav3[0][0] == 0);
+        CHECK(sav3[1][0] == 2);
+        CHECK_THROWS_AS(sav3[1][1], fail_fast);
+        CHECK_THROWS_AS(sav3[0][1], fail_fast);
+    }
+
+    // retype strided array with not enough elements - last dimension of the array is too small
+    {
+        strided_bounds<2> bounds{{4, 2}, {4, 1}};
+        multi_span<const byte, 2, dynamic_range> bytes2 =
+            as_multi_span(bytes, dim<2>(), dim(bytes.size() / 2));
+        strided_span<const byte, 2> sav2{bytes2, bounds};
+        CHECK_THROWS_AS(sav2.as_strided_span<int>(), fail_fast);
+    }
+
+    // retype strided array with not enough elements - strides are too small
+    {
+        strided_bounds<2> bounds{{4, 2}, {2, 1}};
+        multi_span<const byte, 2, dynamic_range> bytes2 =
+            as_multi_span(bytes, dim<2>(), dim(bytes.size() / 2));
+        strided_span<const byte, 2> sav2{bytes2, bounds};
+        CHECK_THROWS_AS(sav2.as_strided_span<int>(), fail_fast);
+    }
+
+    // retype strided array with not enough elements - last dimension does not divide by the new
+    // typesize
+    {
+        strided_bounds<2> bounds{{2, 6}, {4, 1}};
+        multi_span<const byte, 2, dynamic_range> bytes2 =
+            as_multi_span(bytes, dim<2>(), dim(bytes.size() / 2));
+        strided_span<const byte, 2> sav2{bytes2, bounds};
+        CHECK_THROWS_AS(sav2.as_strided_span<int>(), fail_fast);
+    }
+
+    // retype strided array with not enough elements - strides does not divide by the new
+    // typesize
+    {
+        strided_bounds<2> bounds{{2, 1}, {6, 1}};
+        multi_span<const byte, 2, dynamic_range> bytes2 =
+            as_multi_span(bytes, dim<2>(), dim(bytes.size() / 2));
+        strided_span<const byte, 2> sav2{bytes2, bounds};
+        CHECK_THROWS_AS(sav2.as_strided_span<int>(), fail_fast);
+    }
+
+    // retype strided array with irregular strides - from raw data
+    {
+        strided_bounds<1> bounds{bytes.size() / 2, 2};
+        strided_span<const byte, 1> sav2{bytes.data(), bytes.size(), bounds};
+        CHECK_THROWS_AS(sav2.as_strided_span<int>(), fail_fast);
+    }
+
+    // retype strided array with irregular strides - from multi_span
+    {
+        strided_bounds<1> bounds{bytes.size() / 2, 2};
+        strided_span<const byte, 1> sav2{bytes, bounds};
+        CHECK_THROWS_AS(sav2.as_strided_span<int>(), fail_fast);
+    }
+}
+
+TEST_CASE("empty_strided_spans")
+{
+    {
+        multi_span<int, 0> empty_av(nullptr);
+        strided_span<int, 1> empty_sav{empty_av, {0, 1}};
+
+        CHECK(empty_sav.bounds().index_bounds() == multi_span_index<1>{0});
+        CHECK_THROWS_AS(empty_sav[0], fail_fast);
+        CHECK_THROWS_AS(empty_sav.begin()[0], fail_fast);
+        CHECK_THROWS_AS(empty_sav.cbegin()[0], fail_fast);
+
+        for (const auto& v : empty_sav) {
+            (void) v;
+            CHECK(false);
+        }
+    }
+
+    {
+        strided_span<int, 1> empty_sav{nullptr, 0, {0, 1}};
+
+        CHECK(empty_sav.bounds().index_bounds() == multi_span_index<1>{0});
+        CHECK_THROWS_AS(empty_sav[0], fail_fast);
+        CHECK_THROWS_AS(empty_sav.begin()[0], fail_fast);
+        CHECK_THROWS_AS(empty_sav.cbegin()[0], fail_fast);
+
+        for (const auto& v : empty_sav) {
+            (void) v;
+            CHECK(false);
+        }
+    }
+}
+
+void iterate_every_other_element(multi_span<int, dynamic_range> av)
+{
+    // pick every other element
+
+    auto length = av.size() / 2;
+#if _MSC_VER > 1800
+    auto bounds = strided_bounds<1>({length}, {2});
+#else
+    auto bounds = strided_bounds<1>(multi_span_index<1>{length}, multi_span_index<1>{2});
+#endif
+    strided_span<int, 1> strided(&av.data()[1], av.size() - 1, bounds);
+
+    CHECK(strided.size() == length);
+    CHECK(strided.bounds().index_bounds()[0] == length);
+    for (auto i = 0; i < strided.size(); ++i) {
+        CHECK(strided[i] == av[2 * i + 1]);
+    }
+
+    int idx = 0;
+    for (auto num : strided) {
+        CHECK(num == av[2 * idx + 1]);
+        idx++;
+    }
+}
+
+TEST_CASE("strided_span_section_iteration")
+{
+    int arr[8] = {4, 0, 5, 1, 6, 2, 7, 3};
+
+    // static bounds
+    {
+        multi_span<int, 8> av(arr, 8);
+        iterate_every_other_element(av);
+    }
+
+    // dynamic bounds
+    {
+        multi_span<int, dynamic_range> av(arr, 8);
+        iterate_every_other_element(av);
+    }
+}
+
+TEST_CASE("dynamic_strided_span_section_iteration")
+{
+    auto arr = new int[8];
+    for (int i = 0; i < 4; ++i) {
+        arr[2 * i] = 4 + i;
+        arr[2 * i + 1] = i;
+    }
+
+    auto av = as_multi_span(arr, 8);
+    iterate_every_other_element(av);
+
+    delete[] arr;
+}
+
+void iterate_second_slice(multi_span<int, dynamic_range, dynamic_range, dynamic_range> av)
+{
+    const int expected[6] = {2, 3, 10, 11, 18, 19};
+    auto section = av.section({0, 1, 0}, {3, 1, 2});
+
+    for (auto i = 0; i < section.extent<0>(); ++i) {
+        for (auto j = 0; j < section.extent<1>(); ++j)
+            for (auto k = 0; k < section.extent<2>(); ++k) {
+                auto idx = multi_span_index<3>{i, j, k}; // avoid braces in the CHECK macro
+                CHECK(section[idx] == expected[2 * i + 2 * j + k]);
+            }
+    }
+
+    for (auto i = 0; i < section.extent<0>(); ++i) {
+        for (auto j = 0; j < section.extent<1>(); ++j)
+            for (auto k = 0; k < section.extent<2>(); ++k)
+                CHECK(section[i][j][k] == expected[2 * i + 2 * j + k]);
+    }
+
+    int i = 0;
+    for (const auto num : section) {
+        CHECK(num == expected[i]);
+        i++;
+    }
+}
+
+TEST_CASE("strided_span_section_iteration_3d")
+{
+    int arr[3][4][2]{};
+    for (auto i = 0; i < 3; ++i) {
+        for (auto j = 0; j < 4; ++j)
+            for (auto k = 0; k < 2; ++k) arr[i][j][k] = 8 * i + 2 * j + k;
+    }
+
+    {
+        multi_span<int, 3, 4, 2> av = arr;
+        iterate_second_slice(av);
+    }
+}
+
+TEST_CASE("dynamic_strided_span_section_iteration_3d")
+{
+    const auto height = 12, width = 2;
+    const auto size = height * width;
+
+    auto arr = new int[static_cast<std::size_t>(size)];
+    for (auto i = 0; i < size; ++i) {
+        arr[i] = i;
+    }
+
+    {
+        auto av = as_multi_span(as_multi_span(arr, 24), dim<3>(), dim<4>(), dim<2>());
+        iterate_second_slice(av);
+    }
+
+    {
+        auto av = as_multi_span(as_multi_span(arr, 24), dim(3), dim<4>(), dim<2>());
+        iterate_second_slice(av);
+    }
+
+    {
+        auto av = as_multi_span(as_multi_span(arr, 24), dim<3>(), dim(4), dim<2>());
+        iterate_second_slice(av);
+    }
+
+    {
+        auto av = as_multi_span(as_multi_span(arr, 24), dim<3>(), dim<4>(), dim(2));
+        iterate_second_slice(av);
+    }
+    delete[] arr;
+}
+
+TEST_CASE("strided_span_conversion")
+{
+    // get an multi_span of 'c' values from the list of X's
+
+    struct X
+    {
+        int a;
+        int b;
+        int c;
+    };
+
+    X arr[4] = {{0, 1, 2}, {3, 4, 5}, {6, 7, 8}, {9, 10, 11}};
+
+    int s = sizeof(int) / sizeof(byte);
+    auto d2 = 3 * s;
+    auto d1 = narrow_cast<int>(sizeof(int)) * 12 / d2;
+
+    // convert to 4x12 array of bytes
+    auto av = as_multi_span(as_bytes(as_multi_span(arr, 4)), dim(d1), dim(d2));
+
+    CHECK(av.bounds().index_bounds()[0] == 4);
+    CHECK(av.bounds().index_bounds()[1] == 12);
+
+    // get the last 4 columns
+    auto section = av.section({0, 2 * s}, {4, s}); // { { arr[0].c[0], arr[0].c[1], arr[0].c[2],
+                                                   // arr[0].c[3] } , { arr[1].c[0], ... } , ...
+                                                   // }
+
+    // convert to array 4x1 array of integers
+    auto cs = section.as_strided_span<int>(); // { { arr[0].c }, {arr[1].c } , ... }
+
+    CHECK(cs.bounds().index_bounds()[0] == 4);
+    CHECK(cs.bounds().index_bounds()[1] == 1);
+
+    // transpose to 1x4 array
+    strided_bounds<2> reverse_bounds{
+        {cs.bounds().index_bounds()[1], cs.bounds().index_bounds()[0]},
+        {cs.bounds().strides()[1], cs.bounds().strides()[0]}};
+
+    strided_span<int, 2> transposed{cs.data(), cs.bounds().total_size(), reverse_bounds};
+
+    // slice to get a one-dimensional array of c's
+    strided_span<int, 1> result = transposed[0];
+
+    CHECK(result.bounds().index_bounds()[0] == 4);
+    CHECK_THROWS_AS(result.bounds().index_bounds()[1], fail_fast);
+
+    int i = 0;
+    for (auto& num : result) {
+        CHECK(num == arr[i].c);
+        i++;
+    }
+}
diff --git a/tests/string_span_tests.cpp b/tests/string_span_tests.cpp
new file mode 100644
index 0000000..c0b5b19
--- /dev/null
+++ b/tests/string_span_tests.cpp
@@ -0,0 +1,1188 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <catch/catch.hpp> // for AssertionHandler, StringRef, CHECK, TEST_...
+
+#include <gsl/gsl_assert>  // for Expects, fail_fast (ptr only)
+#include <gsl/pointers>    // for owner
+#include <gsl/span>        // for span, dynamic_extent
+#include <gsl/string_span> // for basic_string_span, operator==, ensure_z
+
+#include <algorithm>   // for move, find
+#include <cstddef>     // for size_t
+#include <map>         // for map
+#include <string>      // for basic_string, string, char_traits, operat...
+#include <type_traits> // for remove_reference<>::type
+#include <vector>      // for vector, allocator
+
+using namespace std;
+using namespace gsl;
+
+// Generic string functions
+
+namespace generic
+{
+
+template <typename CharT>
+auto strlen(const CharT* s)
+{
+    auto p = s;
+    while (*p) ++p;
+    return p - s;
+}
+
+template <typename CharT>
+auto strnlen(const CharT* s, std::size_t n)
+{
+    return std::find(s, s + n, CharT(0)) - s;
+}
+
+} // namespace generic
+
+TEST_CASE("TestLiteralConstruction")
+{
+    cwstring_span<> v = ensure_z(L"Hello");
+    CHECK(5 == v.length());
+
+#ifdef CONFIRM_COMPILATION_ERRORS
+    wstring_span<> v2 = ensure0(L"Hello");
+#endif
+}
+
+TEST_CASE("TestConstructFromStdString")
+{
+    std::string s = "Hello there world";
+    cstring_span<> v = s;
+    CHECK(v.length() == static_cast<cstring_span<>::index_type>(s.length()));
+}
+
+TEST_CASE("TestConstructFromStdVector")
+{
+    std::vector<char> vec(5, 'h');
+    string_span<> v{vec};
+    CHECK(v.length() == static_cast<string_span<>::index_type>(vec.size()));
+}
+
+TEST_CASE("TestStackArrayConstruction")
+{
+    wchar_t stack_string[] = L"Hello";
+
+    {
+        cwstring_span<> v = ensure_z(stack_string);
+        CHECK(v.length() == 5);
+    }
+
+    {
+        cwstring_span<> v = stack_string;
+        CHECK(v.length() == 5);
+    }
+
+    {
+        wstring_span<> v = ensure_z(stack_string);
+        CHECK(v.length() == 5);
+    }
+
+    {
+        wstring_span<> v = stack_string;
+        CHECK(v.length() == 5);
+    }
+}
+
+TEST_CASE("TestConstructFromConstCharPointer")
+{
+    const char* s = "Hello";
+    cstring_span<> v = ensure_z(s);
+    CHECK(v.length() == 5);
+}
+
+TEST_CASE("TestConversionToConst")
+{
+    char stack_string[] = "Hello";
+    string_span<> v = ensure_z(stack_string);
+    cstring_span<> v2 = v;
+    CHECK(v.length() == v2.length());
+}
+
+TEST_CASE("TestConversionFromConst")
+{
+    char stack_string[] = "Hello";
+    cstring_span<> v = ensure_z(stack_string);
+    (void) v;
+#ifdef CONFIRM_COMPILATION_ERRORS
+    string_span<> v2 = v;
+    string_span<> v3 = "Hello";
+#endif
+}
+
+TEST_CASE("TestToString")
+{
+    auto s = gsl::to_string(cstring_span<>{});
+    CHECK(s.length() == 0);
+
+    char stack_string[] = "Hello";
+    cstring_span<> v = ensure_z(stack_string);
+    auto s2 = gsl::to_string(v);
+    CHECK(static_cast<cstring_span<>::index_type>(s2.length()) == v.length());
+    CHECK(s2.length() == 5);
+}
+
+TEST_CASE("TestToBasicString")
+{
+    auto s = gsl::to_basic_string<char, std::char_traits<char>, ::std::allocator<char>>(
+        cstring_span<>{});
+    CHECK(s.length() == 0);
+
+    char stack_string[] = "Hello";
+    cstring_span<> v = ensure_z(stack_string);
+    auto s2 = gsl::to_basic_string<char, std::char_traits<char>, ::std::allocator<char>>(v);
+    CHECK(static_cast<cstring_span<>::index_type>(s2.length()) == v.length());
+    CHECK(s2.length() == 5);
+}
+
+TEST_CASE("EqualityAndImplicitConstructors")
+{
+    {
+        cstring_span<> span = "Hello";
+        cstring_span<> span1;
+
+        // comparison to empty span
+        CHECK(span1 != span);
+        CHECK(span != span1);
+    }
+
+    {
+        cstring_span<> span = "Hello";
+        cstring_span<> span1 = "Hello1";
+
+        // comparison to different span
+        CHECK(span1 != span);
+        CHECK(span != span1);
+    }
+
+    {
+        cstring_span<> span = "Hello";
+
+        const char ar[] = {'H', 'e', 'l', 'l', 'o'};
+        const char ar1[] = "Hello";
+        const char ar2[10] = "Hello";
+        const char* ptr = "Hello";
+        const std::string str = "Hello";
+        const std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        gsl::span<const char> sp = ensure_z("Hello");
+
+        // comparison to  literal
+        CHECK(span == cstring_span<>("Hello"));
+
+        // comparison to static array with no null termination
+        CHECK(span == cstring_span<>(ar));
+
+        // comparison to static array with null at the end
+        CHECK(span == cstring_span<>(ar1));
+
+        // comparison to static array with null in the middle
+        CHECK(span == cstring_span<>(ar2));
+
+        // comparison to null-terminated c string
+        CHECK(span == cstring_span<>(ptr, 5));
+
+        // comparison to string
+        CHECK(span == cstring_span<>(str));
+
+        // comparison to vector of charaters with no null termination
+        CHECK(span == cstring_span<>(vec));
+
+        // comparison to span
+        CHECK(span == cstring_span<>(sp));
+
+        // comparison to string_span
+        CHECK(span == span);
+    }
+
+    {
+        char ar[] = {'H', 'e', 'l', 'l', 'o'};
+
+        string_span<> span = ar;
+
+        char ar1[] = "Hello";
+        char ar2[10] = "Hello";
+        char* ptr = ar;
+        std::string str = "Hello";
+        std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        gsl::span<char> sp = ensure_z(ar1);
+
+        // comparison to static array with no null termination
+        CHECK(span == string_span<>(ar));
+
+        // comparison to static array with null at the end
+        CHECK(span == string_span<>(ar1));
+
+        // comparison to static array with null in the middle
+        CHECK(span == string_span<>(ar2));
+
+        // comparison to null-terminated c string
+        CHECK(span == string_span<>(ptr, 5));
+
+        // comparison to string
+        CHECK(span == string_span<>(str));
+
+        // comparison to vector of charaters with no null termination
+        CHECK(span == string_span<>(vec));
+
+        // comparison to span
+        CHECK(span == string_span<>(sp));
+
+        // comparison to string_span
+        CHECK(span == span);
+    }
+
+    {
+        const char ar[] = {'H', 'e', 'l', 'l', 'o'};
+        const char ar1[] = "Hello";
+        const char ar2[10] = "Hello";
+        const std::string str = "Hello";
+        const std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        const gsl::span<const char> sp = ensure_z("Hello");
+
+        cstring_span<> span = "Hello";
+
+        // const span, const other type
+
+        CHECK(span == "Hello");
+        CHECK(span == ar);
+        CHECK(span == ar1);
+        CHECK(span == ar2);
+#ifdef CONFIRM_COMPILATION_ERRORS
+        const char* ptr = "Hello";
+        CHECK(span == ptr);
+#endif
+        CHECK(span == str);
+        CHECK(span == vec);
+        CHECK(span == sp);
+
+        CHECK("Hello" == span);
+        CHECK(ar == span);
+        CHECK(ar1 == span);
+        CHECK(ar2 == span);
+#ifdef CONFIRM_COMPILATION_ERRORS
+        CHECK(ptr == span);
+#endif
+        CHECK(str == span);
+        CHECK(vec == span);
+        CHECK(sp == span);
+
+        // const span, non-const other type
+
+        char _ar[] = {'H', 'e', 'l', 'l', 'o'};
+        char _ar1[] = "Hello";
+        char _ar2[10] = "Hello";
+        char* _ptr = _ar;
+        std::string _str = "Hello";
+        std::vector<char> _vec = {'H', 'e', 'l', 'l', 'o'};
+        gsl::span<char> _sp{_ar, 5};
+
+        CHECK(span == _ar);
+        CHECK(span == _ar1);
+        CHECK(span == _ar2);
+#ifdef CONFIRM_COMPILATION_ERRORS
+        CHECK(span == _ptr);
+#endif
+        CHECK(span == _str);
+        CHECK(span == _vec);
+        CHECK(span == _sp);
+
+        CHECK(_ar == span);
+        CHECK(_ar1 == span);
+        CHECK(_ar2 == span);
+#ifdef CONFIRM_COMPILATION_ERRORS
+        CHECK(_ptr == span);
+#endif
+        CHECK(_str == span);
+        CHECK(_vec == span);
+        CHECK(_sp == span);
+
+        string_span<> _span{_ptr, 5};
+
+        // non-const span, non-const other type
+
+        CHECK(_span == _ar);
+        CHECK(_span == _ar1);
+        CHECK(_span == _ar2);
+#ifdef CONFIRM_COMPILATION_ERRORS
+        CHECK(_span == _ptr);
+#endif
+        CHECK(_span == _str);
+        CHECK(_span == _vec);
+        CHECK(_span == _sp);
+
+        CHECK(_ar == _span);
+        CHECK(_ar1 == _span);
+        CHECK(_ar2 == _span);
+#ifdef CONFIRM_COMPILATION_ERRORS
+        CHECK(_ptr == _span);
+#endif
+        CHECK(_str == _span);
+        CHECK(_vec == _span);
+        CHECK(_sp == _span);
+
+        // non-const span, const other type
+
+        CHECK(_span == "Hello");
+        CHECK(_span == ar);
+        CHECK(_span == ar1);
+        CHECK(_span == ar2);
+#ifdef CONFIRM_COMPILATION_ERRORS
+        CHECK(_span == ptr);
+#endif
+        CHECK(_span == str);
+        CHECK(_span == vec);
+        CHECK(_span == sp);
+
+        CHECK("Hello" == _span);
+        CHECK(ar == _span);
+        CHECK(ar1 == _span);
+        CHECK(ar2 == _span);
+#ifdef CONFIRM_COMPILATION_ERRORS
+        CHECK(ptr == _span);
+#endif
+        CHECK(str == _span);
+        CHECK(vec == _span);
+        CHECK(sp == _span);
+
+        // two spans
+
+        CHECK(_span == span);
+        CHECK(span == _span);
+    }
+
+    {
+        std::vector<char> str1 = {'H', 'e', 'l', 'l', 'o'};
+        cstring_span<> span1 = str1;
+        std::vector<char> str2 = std::move(str1);
+        cstring_span<> span2 = str2;
+
+        // comparison of spans from the same vector before and after move (ok)
+        CHECK(span1 == span2);
+    }
+}
+
+TEST_CASE("ComparisonAndImplicitConstructors")
+{
+    {
+        cstring_span<> span = "Hello";
+
+        const char ar[] = {'H', 'e', 'l', 'l', 'o'};
+        const char ar1[] = "Hello";
+        const char ar2[10] = "Hello";
+        const char* ptr = "Hello";
+        const std::string str = "Hello";
+        const std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+
+        // comparison to  literal
+        CHECK(span < cstring_span<>("Helloo"));
+        CHECK(span > cstring_span<>("Hell"));
+
+        // comparison to static array with no null termination
+        CHECK(span >= cstring_span<>(ar));
+
+        // comparison to static array with null at the end
+        CHECK(span <= cstring_span<>(ar1));
+
+        // comparison to static array with null in the middle
+        CHECK(span >= cstring_span<>(ar2));
+
+        // comparison to null-terminated c string
+        CHECK(span <= cstring_span<>(ptr, 5));
+
+        // comparison to string
+        CHECK(span >= cstring_span<>(str));
+
+        // comparison to vector of charaters with no null termination
+        CHECK(span <= cstring_span<>(vec));
+    }
+
+    {
+        char ar[] = {'H', 'e', 'l', 'l', 'o'};
+
+        string_span<> span = ar;
+
+        char larr[] = "Hell";
+        char rarr[] = "Helloo";
+
+        char ar1[] = "Hello";
+        char ar2[10] = "Hello";
+        char* ptr = ar;
+        std::string str = "Hello";
+        std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+
+        // comparison to static array with no null termination
+        CHECK(span <= string_span<>(ar));
+        CHECK(span < string_span<>(rarr));
+        CHECK(span > string_span<>(larr));
+
+        // comparison to static array with null at the end
+        CHECK(span >= string_span<>(ar1));
+
+        // comparison to static array with null in the middle
+        CHECK(span <= string_span<>(ar2));
+
+        // comparison to null-terminated c string
+        CHECK(span >= string_span<>(ptr, 5));
+
+        // comparison to string
+        CHECK(span <= string_span<>(str));
+
+        // comparison to vector of charaters with no null termination
+        CHECK(span >= string_span<>(vec));
+    }
+}
+TEST_CASE("ConstrutorsEnsureZ")
+{
+    // remove z from literals
+    {
+        cstring_span<> sp = "hello";
+        CHECK((sp.length() == 5));
+    }
+
+    // take the string as is
+    {
+        auto str = std::string("hello");
+        cstring_span<> sp = str;
+        CHECK((sp.length() == 5));
+    }
+
+    // ensure z on c strings
+    {
+        gsl::owner<char*> ptr = new char[3];
+
+        ptr[0] = 'a';
+        ptr[1] = 'b';
+        ptr[2] = '\0';
+
+        string_span<> span = ensure_z(ptr);
+        CHECK(span.length() == 2);
+
+        delete[] ptr;
+    }
+}
+
+TEST_CASE("Constructors")
+{
+    // creating cstring_span
+
+    // from span of a final extent
+    {
+        span<const char, 6> sp = "Hello";
+        cstring_span<> span = sp;
+        CHECK(span.length() == 6);
+    }
+
+// from const span of a final extent to non-const string_span
+#ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        span<const char, 6> sp = "Hello";
+        string_span<> span = sp;
+        CHECK(span.length() == 6);
+    }
+#endif
+
+// from string temporary
+#ifdef CONFIRM_COMPILATION_ERRORS
+    {
+        cstring_span<> span = std::string("Hello");
+    }
+#endif
+
+    // default
+    {
+        cstring_span<> span;
+        CHECK(span.length() == 0);
+    }
+
+    // from string literal
+    {
+        cstring_span<> span = "Hello";
+        CHECK(span.length() == 5);
+    }
+
+    // from const static array
+    {
+        const char ar[] = {'H', 'e', 'l', 'l', 'o'};
+        cstring_span<> span = ar;
+        CHECK(span.length() == 5);
+    }
+
+    // from non-const static array
+    {
+        char ar[] = {'H', 'e', 'l', 'l', 'o'};
+        cstring_span<> span = ar;
+        CHECK(span.length() == 5);
+    }
+
+    // from const ptr and length
+    {
+        const char* ptr = "Hello";
+        cstring_span<> span{ptr, 5};
+        CHECK(span.length() == 5);
+    }
+
+    // from const ptr and length, include 0
+    {
+        const char* ptr = "Hello";
+        cstring_span<> span{ptr, 6};
+        CHECK(span.length() == 6);
+    }
+
+    // from const ptr and length, 0 inside
+    {
+        const char* ptr = "He\0lo";
+        cstring_span<> span{ptr, 5};
+        CHECK(span.length() == 5);
+    }
+
+    // from non-const ptr and length
+    {
+        char ar[] = {'H', 'e', 'l', 'l', 'o'};
+        char* ptr = ar;
+        cstring_span<> span{ptr, 5};
+        CHECK(span.length() == 5);
+    }
+
+    // from non-const ptr and length, 0 inside
+    {
+        char ar[] = {'H', 'e', '\0', 'l', 'o'};
+        char* ptr = ar;
+        cstring_span<> span{ptr, 5};
+        CHECK(span.length() == 5);
+    }
+
+    // from const string
+    {
+        const std::string str = "Hello";
+        const cstring_span<> span = str;
+        CHECK(span.length() == 5);
+    }
+
+    // from non-const string
+    {
+        std::string str = "Hello";
+        const cstring_span<> span = str;
+        CHECK(span.length() == 5);
+    }
+
+    // from const vector
+    {
+        const std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        const cstring_span<> span = vec;
+        CHECK(span.length() == 5);
+    }
+
+    // from non-const vector
+    {
+        std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        const cstring_span<> span = vec;
+        CHECK(span.length() == 5);
+    }
+
+    // from const span
+    {
+        const std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        const span<const char> inner = vec;
+        const cstring_span<> span = inner;
+        CHECK(span.length() == 5);
+    }
+
+    // from non-const span
+    {
+        std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        const span<char> inner = vec;
+        const cstring_span<> span = inner;
+        CHECK(span.length() == 5);
+    }
+
+    // from const string_span
+    {
+        const std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        const cstring_span<> tmp = vec;
+        const cstring_span<> span = tmp;
+        CHECK(span.length() == 5);
+    }
+
+    // from non-const string_span
+    {
+        std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        string_span<> tmp = vec;
+        cstring_span<> span = tmp;
+        CHECK(span.length() == 5);
+    }
+
+    // creating string_span
+
+    // from string literal
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        string_span<> span = "Hello";
+#endif
+    }
+
+    // from const static array
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        const char ar[] = {'H', 'e', 'l', 'l', 'o'};
+        string_span<> span = ar;
+        CHECK(span.length() == 5);
+#endif
+    }
+
+    // from non-const static array
+    {
+        char ar[] = {'H', 'e', 'l', 'l', 'o'};
+        string_span<> span = ar;
+        CHECK(span.length() == 5);
+    }
+
+    // from const ptr and length
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        const char* ptr = "Hello";
+        string_span<> span{ptr, 5};
+        CHECK(span.length() == 5);
+#endif
+    }
+
+    // from non-const ptr and length
+    {
+        char ar[] = {'H', 'e', 'l', 'l', 'o'};
+        char* ptr = ar;
+        string_span<> span{ptr, 5};
+        CHECK(span.length() == 5);
+    }
+
+    // from const string
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        const std::string str = "Hello";
+        string_span<> span = str;
+        CHECK(span.length() == 5);
+#endif
+    }
+
+    // from non-const string
+    {
+        std::string str = "Hello";
+        string_span<> span = str;
+        CHECK(span.length() == 5);
+    }
+
+    // from const vector
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        const std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        string_span<> span = vec;
+        CHECK(span.length() == 5);
+#endif
+    }
+
+    // from non-const vector
+    {
+        std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        string_span<> span = vec;
+        CHECK(span.length() == 5);
+    }
+
+    // from const span
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        const span<const char> inner = vec;
+        string_span<> span = inner;
+        CHECK(span.length() == 5);
+#endif
+    }
+
+    // from non-const span
+    {
+        std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        span<char> inner = vec;
+        string_span<> span = inner;
+        CHECK(span.length() == 5);
+    }
+
+    // from non-const span of non-const data from const vector
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        const std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        const span<char> inner = vec;
+        string_span<> span = inner;
+        CHECK(span.length() == 5);
+#endif
+    }
+
+    // from const string_span
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        cstring_span<> tmp = vec;
+        string_span<> span = tmp;
+        CHECK(span.length() == 5);
+#endif
+    }
+
+    // from non-const string_span
+    {
+        std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        const string_span<> tmp = vec;
+        const string_span<> span = tmp;
+        CHECK(span.length() == 5);
+    }
+
+    // from non-const string_span from const vector
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        const std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        string_span<> tmp = vec;
+        string_span<> span = tmp;
+        CHECK(span.length() == 5);
+#endif
+    }
+
+    // from const string_span of non-const data
+    {
+        std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        const string_span<> tmp = vec;
+        const string_span<> span = tmp;
+        CHECK(span.length() == 5);
+    }
+}
+
+template <typename T>
+T move_wrapper(T&& t)
+{
+    return std::move(t);
+}
+
+template <class T>
+T create()
+{
+    return T{};
+}
+
+template <class T>
+void use(basic_string_span<T, gsl::dynamic_extent>)
+{
+}
+
+TEST_CASE("MoveConstructors")
+{
+    // move string_span
+    {
+        cstring_span<> span = "Hello";
+        const auto span1 = std::move(span);
+        CHECK(span1.length() == 5);
+    }
+    {
+        cstring_span<> span = "Hello";
+        const auto span1 = move_wrapper(std::move(span));
+        CHECK(span1.length() == 5);
+    }
+    {
+        cstring_span<> span = "Hello";
+        const auto span1 = move_wrapper(std::move(span));
+        CHECK(span1.length() == 5);
+    }
+
+    // move span
+    {
+        span<const char> span = ensure_z("Hello");
+        const cstring_span<> span1 = std::move(span);
+        CHECK(span1.length() == 5);
+    }
+    {
+        span<const char> span = ensure_z("Hello");
+        const cstring_span<> span2 = move_wrapper(std::move(span));
+        CHECK(span2.length() == 5);
+    }
+
+    // move string
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        std::string str = "Hello";
+        string_span<> span = std::move(str);
+        CHECK(span.length() == 5);
+#endif
+    }
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        std::string str = "Hello";
+        string_span<> span = move_wrapper<std::string>(std::move(str));
+        CHECK(span.length() == 5);
+#endif
+    }
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        use<char>(create<string>());
+#endif
+    }
+
+    // move container
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        string_span<> span = std::move(vec);
+        CHECK(span.length() == 5);
+#endif
+    }
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        std::vector<char> vec = {'H', 'e', 'l', 'l', 'o'};
+        string_span<> span = move_wrapper<std::vector<char>>(std::move(vec));
+        CHECK(span.length() == 5);
+#endif
+    }
+    {
+#ifdef CONFIRM_COMPILATION_ERRORS
+        use<char>(create<std::vector<char>>());
+#endif
+    }
+}
+
+TEST_CASE("Conversion")
+{
+#ifdef CONFIRM_COMPILATION_ERRORS
+    cstring_span<> span = "Hello";
+    cwstring_span<> wspan{span};
+    CHECK(wspan.length() == 5);
+#endif
+}
+
+czstring_span<> CreateTempName(string_span<> span)
+{
+    Expects(span.size() > 1);
+
+    int last = 0;
+    if (span.size() > 4) {
+        span[0] = 't';
+        span[1] = 'm';
+        span[2] = 'p';
+        last = 3;
+    }
+    span[last] = '\0';
+
+    auto ret = span.subspan(0, 4);
+    return {ret};
+}
+
+TEST_CASE("zstring")
+{
+
+    // create zspan from zero terminated string
+    {
+        char buf[1];
+        buf[0] = '\0';
+
+        zstring_span<> zspan({buf, 1});
+
+        CHECK(generic::strlen(zspan.assume_z()) == 0);
+        CHECK(zspan.as_string_span().size() == 0);
+        CHECK(zspan.ensure_z().size() == 0);
+    }
+
+    // create zspan from non-zero terminated string
+    {
+        char buf[1];
+        buf[0] = 'a';
+
+        auto workaround_macro = [&]() { zstring_span<> zspan({buf, 1}); };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    }
+
+    // usage scenario: create zero-terminated temp file name and pass to a legacy API
+    {
+        char buf[10];
+
+        auto name = CreateTempName({buf, 10});
+        if (!name.empty()) {
+            czstring<> str = name.assume_z();
+            CHECK(generic::strlen(str) == 3);
+            CHECK(*(str + 3) == '\0');
+        }
+    }
+}
+
+cwzstring_span<> CreateTempNameW(wstring_span<> span)
+{
+    Expects(span.size() > 1);
+
+    int last = 0;
+    if (span.size() > 4) {
+        span[0] = L't';
+        span[1] = L'm';
+        span[2] = L'p';
+        last = 3;
+    }
+    span[last] = L'\0';
+
+    auto ret = span.subspan(0, 4);
+    return {ret};
+}
+
+TEST_CASE("wzstring")
+{
+
+    // create zspan from zero terminated string
+    {
+        wchar_t buf[1];
+        buf[0] = L'\0';
+
+        wzstring_span<> zspan({buf, 1});
+
+        CHECK(generic::strnlen(zspan.assume_z(), 1) == 0);
+        CHECK(zspan.as_string_span().size() == 0);
+        CHECK(zspan.ensure_z().size() == 0);
+    }
+
+    // create zspan from non-zero terminated string
+    {
+        wchar_t buf[1];
+        buf[0] = L'a';
+
+        const auto workaround_macro = [&]() { wzstring_span<> zspan({buf, 1}); };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    }
+
+    // usage scenario: create zero-terminated temp file name and pass to a legacy API
+    {
+        wchar_t buf[10];
+
+        const auto name = CreateTempNameW({buf, 10});
+        if (!name.empty()) {
+            cwzstring<> str = name.assume_z();
+            CHECK(generic::strnlen(str, 10) == 3);
+            CHECK(*(str + 3) == L'\0');
+        }
+    }
+}
+
+cu16zstring_span<> CreateTempNameU16(u16string_span<> span)
+{
+    Expects(span.size() > 1);
+
+    int last = 0;
+    if (span.size() > 4) {
+        span[0] = u't';
+        span[1] = u'm';
+        span[2] = u'p';
+        last = 3;
+    }
+    span[last] = u'\0';
+
+    auto ret = span.subspan(0, 4);
+    return {ret};
+}
+
+TEST_CASE("u16zstring")
+{
+
+    // create zspan from zero terminated string
+    {
+        char16_t buf[1];
+        buf[0] = L'\0';
+
+        u16zstring_span<> zspan({buf, 1});
+
+        CHECK(generic::strnlen(zspan.assume_z(), 1) == 0);
+        CHECK(zspan.as_string_span().size() == 0);
+        CHECK(zspan.ensure_z().size() == 0);
+    }
+
+    // create zspan from non-zero terminated string
+    {
+        char16_t buf[1];
+        buf[0] = u'a';
+
+        const auto workaround_macro = [&]() { u16zstring_span<> zspan({buf, 1}); };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    }
+
+    // usage scenario: create zero-terminated temp file name and pass to a legacy API
+    {
+        char16_t buf[10];
+
+        const auto name = CreateTempNameU16({buf, 10});
+        if (!name.empty()) {
+            cu16zstring<> str = name.assume_z();
+            CHECK(generic::strnlen(str, 10) == 3);
+            CHECK(*(str + 3) == L'\0');
+        }
+    }
+}
+
+cu32zstring_span<> CreateTempNameU32(u32string_span<> span)
+{
+    Expects(span.size() > 1);
+
+    int last = 0;
+    if (span.size() > 4) {
+        span[0] = U't';
+        span[1] = U'm';
+        span[2] = U'p';
+        last = 3;
+    }
+    span[last] = U'\0';
+
+    auto ret = span.subspan(0, 4);
+    return {ret};
+}
+
+TEST_CASE("u32zstring")
+{
+
+    // create zspan from zero terminated string
+    {
+        char32_t buf[1];
+        buf[0] = L'\0';
+
+        u32zstring_span<> zspan({buf, 1});
+
+        CHECK(generic::strnlen(zspan.assume_z(), 1) == 0);
+        CHECK(zspan.as_string_span().size() == 0);
+        CHECK(zspan.ensure_z().size() == 0);
+    }
+
+    // create zspan from non-zero terminated string
+    {
+        char32_t buf[1];
+        buf[0] = u'a';
+
+        const auto workaround_macro = [&]() { u32zstring_span<> zspan({buf, 1}); };
+        CHECK_THROWS_AS(workaround_macro(), fail_fast);
+    }
+
+    // usage scenario: create zero-terminated temp file name and pass to a legacy API
+    {
+        char32_t buf[10];
+
+        const auto name = CreateTempNameU32({buf, 10});
+        if (!name.empty()) {
+            cu32zstring<> str = name.assume_z();
+            CHECK(generic::strnlen(str, 10) == 3);
+            CHECK(*(str + 3) == L'\0');
+        }
+    }
+}
+
+TEST_CASE("Issue305")
+{
+    std::map<gsl::cstring_span<>, int> foo = {{"foo", 0}, {"bar", 1}};
+    CHECK(foo["foo"] == 0);
+    CHECK(foo["bar"] == 1);
+}
+
+TEST_CASE("char16_t type")
+{
+    gsl::cu16string_span<> ss1 = gsl::ensure_z(u"abc");
+    CHECK(ss1.size() == 3);
+    CHECK(ss1.size_bytes() == 6);
+
+    std::u16string s1 = gsl::to_string(ss1);
+    CHECK(s1 == u"abc");
+
+    std::u16string s2 = u"abc";
+    gsl::u16string_span<> ss2 = s2;
+    CHECK(ss2.size() == 3);
+
+    gsl::u16string_span<> ss3 = ss2.subspan(1, 1);
+    CHECK(ss3.size() == 1);
+    CHECK(ss3[0] == u'b');
+
+    char16_t buf[4]{u'a', u'b', u'c', u'\0'};
+    gsl::u16string_span<> ss4{buf, 4};
+    CHECK(ss4[3] == u'\0');
+
+    gsl::cu16zstring_span<> ss5(u"abc");
+    CHECK(ss5.as_string_span().size() == 3);
+
+    gsl::cu16string_span<> ss6 = ss5.as_string_span();
+    CHECK(ss6 == ss1);
+
+    std::vector<char16_t> v7 = {u'a', u'b', u'c'};
+    gsl::cu16string_span<> ss7{v7};
+    CHECK(ss7 == ss1);
+
+    gsl::cu16string_span<> ss8 = gsl::ensure_z(u"abc");
+    gsl::cu16string_span<> ss9 = gsl::ensure_z(u"abc");
+    CHECK(ss8 == ss9);
+
+    ss9 = gsl::ensure_z(u"abd");
+    CHECK(ss8 < ss9);
+    CHECK(ss8 <= ss9);
+    CHECK(ss8 != ss9);
+}
+
+TEST_CASE("char32_t type")
+{
+    gsl::cu32string_span<> ss1 = gsl::ensure_z(U"abc");
+    CHECK(ss1.size() == 3);
+    CHECK(ss1.size_bytes() == 12);
+
+    std::u32string s1 = gsl::to_string(ss1);
+    CHECK(s1 == U"abc");
+
+    std::u32string s2 = U"abc";
+    gsl::u32string_span<> ss2 = s2;
+    CHECK(ss2.size() == 3);
+
+    gsl::u32string_span<> ss3 = ss2.subspan(1, 1);
+    CHECK(ss3.size() == 1);
+    CHECK(ss3[0] == U'b');
+
+    char32_t buf[4]{U'a', U'b', U'c', U'\0'};
+    gsl::u32string_span<> ss4{buf, 4};
+    CHECK(ss4[3] == u'\0');
+
+    gsl::cu32zstring_span<> ss5(U"abc");
+    CHECK(ss5.as_string_span().size() == 3);
+
+    gsl::cu32string_span<> ss6 = ss5.as_string_span();
+    CHECK(ss6 == ss1);
+
+    gsl::cu32string_span<> ss8 = gsl::ensure_z(U"abc");
+    gsl::cu32string_span<> ss9 = gsl::ensure_z(U"abc");
+    CHECK(ss8 == ss9);
+
+    ss9 = gsl::ensure_z(U"abd");
+    CHECK(ss8 < ss9);
+    CHECK(ss8 <= ss9);
+    CHECK(ss8 != ss9);
+}
+
+TEST_CASE("as_bytes")
+{
+    cwzstring_span<> v(L"qwerty");
+    const auto s = v.as_string_span();
+    const auto bs = as_bytes(s);
+    CHECK(static_cast<const void*>(bs.data()) == static_cast<const void*>(s.data()));
+    CHECK(bs.size() == s.size_bytes());
+}
+
+TEST_CASE("as_writeable_bytes")
+{
+    wchar_t buf[]{L"qwerty"};
+    wzstring_span<> v(buf);
+    const auto s = v.as_string_span();
+    const auto bs = as_writeable_bytes(s);
+    CHECK(static_cast<const void*>(bs.data()) == static_cast<const void*>(s.data()));
+    CHECK(bs.size() == s.size_bytes());
+}
diff --git a/tests/test.cpp b/tests/test.cpp
new file mode 100644
index 0000000..bae194d
--- /dev/null
+++ b/tests/test.cpp
@@ -0,0 +1,18 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#define CATCH_CONFIG_MAIN
+#include <catch/catch.hpp>
diff --git a/tests/utils_tests.cpp b/tests/utils_tests.cpp
new file mode 100644
index 0000000..587b0a1
--- /dev/null
+++ b/tests/utils_tests.cpp
@@ -0,0 +1,120 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <catch/catch.hpp> // for AssertionHandler, StringRef, CHECK, TEST_...
+
+#include <gsl/gsl_util> // for narrow, finally, narrow_cast, narrowing_e...
+
+#include <algorithm>   // for move
+#include <functional>  // for reference_wrapper, _Bind_helper<>::type
+#include <limits>      // for numeric_limits
+#include <stdint.h>    // for uint32_t, int32_t
+#include <type_traits> // for is_same
+
+using namespace gsl;
+
+TEST_CASE("sanity check for gsl::index typedef")
+{
+    static_assert(std::is_same<gsl::index, std::ptrdiff_t>::value,
+                  "gsl::index represents wrong arithmetic type");
+}
+
+void f(int& i) { i += 1; }
+
+TEST_CASE("finally_lambda")
+{
+    int i = 0;
+    {
+        auto _ = finally([&]() { f(i); });
+        CHECK(i == 0);
+    }
+    CHECK(i == 1);
+}
+
+TEST_CASE("finally_lambda_move")
+{
+    int i = 0;
+    {
+        auto _1 = finally([&]() { f(i); });
+        {
+            auto _2 = std::move(_1);
+            CHECK(i == 0);
+        }
+        CHECK(i == 1);
+        {
+            auto _2 = std::move(_1);
+            CHECK(i == 1);
+        }
+        CHECK(i == 1);
+    }
+    CHECK(i == 1);
+}
+
+TEST_CASE("finally_function_with_bind")
+{
+    int i = 0;
+    {
+        auto _ = finally(std::bind(&f, std::ref(i)));
+        CHECK(i == 0);
+    }
+    CHECK(i == 1);
+}
+
+int j = 0;
+void g() { j += 1; }
+TEST_CASE("finally_function_ptr")
+{
+    j = 0;
+    {
+        auto _ = finally(&g);
+        CHECK(j == 0);
+    }
+    CHECK(j == 1);
+}
+
+TEST_CASE("narrow_cast")
+{
+    int n = 120;
+    char c = narrow_cast<char>(n);
+    CHECK(c == 120);
+
+    n = 300;
+    unsigned char uc = narrow_cast<unsigned char>(n);
+    CHECK(uc == 44);
+}
+
+TEST_CASE("narrow")
+{
+    int n = 120;
+    const char c = narrow<char>(n);
+    CHECK(c == 120);
+
+    n = 300;
+    CHECK_THROWS_AS(narrow<char>(n), narrowing_error);
+
+    const auto int32_max = std::numeric_limits<int32_t>::max();
+    const auto int32_min = std::numeric_limits<int32_t>::min();
+
+    CHECK(narrow<uint32_t>(int32_t(0)) == 0);
+    CHECK(narrow<uint32_t>(int32_t(1)) == 1);
+    CHECK(narrow<uint32_t>(int32_max) == static_cast<uint32_t>(int32_max));
+
+    CHECK_THROWS_AS(narrow<uint32_t>(int32_t(-1)), narrowing_error);
+    CHECK_THROWS_AS(narrow<uint32_t>(int32_min), narrowing_error);
+
+    n = -42;
+    CHECK_THROWS_AS(narrow<unsigned>(n), narrowing_error);
+}